feat(storage): pluggable s3-or-filesystem backend + migration CLI + admin UI

Phase 6a from docs/berth-recommender-and-pdf-plan.md §4.7a + §14.9a. Lays
the storage groundwork for Phase 6b/7 file-bearing schemas (per-berth PDFs,
brochures) without touching those domains yet.

New files:
- src/lib/storage/index.ts        StorageBackend interface + per-process
                                  factory keyed on system_settings.
- src/lib/storage/s3.ts           S3-compatible backend (MinIO/AWS/B2/R2/
                                  Wasabi/Tigris) wrapping the existing minio
                                  JS client. Includes a healthCheck() used
                                  by the admin "Test connection" button.
- src/lib/storage/filesystem.ts   Local filesystem backend with all §14.9a
                                  mitigations baked in.
- src/lib/storage/migrate.ts      Shared migration core — pg_advisory_lock,
                                  per-row resumable progress markers,
                                  sha256 round-trip verification, atomic
                                  storage_backend flip on success.
- scripts/migrate-storage.ts      Thin CLI shim around runMigration().
- src/app/api/storage/[token]/route.ts
                                  Filesystem proxy GET. Verifies HMAC,
                                  enforces single-use replay protection
                                  via Redis SET NX, streams via NextResponse
                                  ReadableStream with explicit Content-Type
                                  + Content-Disposition. Node runtime only.
- src/app/api/v1/admin/storage/route.ts
                                  GET status + POST connection test.
- src/app/api/v1/admin/storage/migrate/route.ts
                                  Super-admin-only POST that runs the
                                  exact same runMigration() as the CLI.
- src/app/(dashboard)/[portSlug]/admin/storage/page.tsx
                                  Super-admin admin UI (current backend,
                                  capacity stats, switch button with
                                  dry-run, test connection, backup hint).
- src/components/admin/storage-admin-panel.tsx
                                  Client component for the page above.

§14.9a critical mitigations implemented:
- Path-traversal: storage keys validated against ^[a-zA-Z0-9/_.-]+$;
  `..`, `.`, `//`, leading `/`, and overlength keys rejected.
- Realpath: storage root realpath'd at create time, every per-key
  resolution checked against the realpath'd prefix.
- Storage root created (or chmod'd) to 0o700.
- Multi-node refusal: FilesystemBackend.create() throws when
  MULTI_NODE_DEPLOYMENT=true.
- HMAC token: sha256-HMAC over the (key, expiry, nonce, filename,
  content-type) payload. Verified with timingSafeEqual; bad sig,
  expired, or invalid-key payloads all return 403.
- Single-use replay: token body cached in Redis SET NX EX 1800s.
- sha256 round-trip: copyAndVerify() re-fetches from the target after
  put() and aborts the migration on any mismatch.
- Free-disk pre-flight: when migrating to filesystem, sums byte counts
  via source.head() and aborts if free space < total * 1.2.
- pg_advisory_lock(0xc7000a01) prevents concurrent migrations.
- Resumable: per-row progress markers in _storage_migration_progress.

system_settings keys read by the factory (jsonb, no schema change):
storage_backend, storage_s3_endpoint, storage_s3_region,
storage_s3_bucket, storage_s3_access_key,
storage_s3_secret_key_encrypted, storage_s3_force_path_style,
storage_filesystem_root, storage_proxy_hmac_secret_encrypted.

Defaults: storage_backend=`s3`, storage_filesystem_root=`./storage`
(./storage added to .gitignore).

Tests added (34 tests, all green):
- tests/unit/storage/filesystem-backend.test.ts — key validation
  allow/reject matrix, realpath escape, 0o700 perms, multi-node
  refusal, HMAC token sign/verify/tamper/expire/invalid-key.
- tests/unit/storage/copy-and-verify.test.ts — sha256 mismatch on
  round-trip aborts the migration.
- tests/integration/storage/proxy-route.test.ts — happy path, wrong
  HMAC secret, expired token, replay rejection.

Phase 6a ships zero file-bearing tables — TABLES_WITH_STORAGE_KEYS is
intentionally empty. berth_pdf_versions and brochure_versions land in
Phase 6b and join the list there. Existing s3_key columns: only
gdpr_export_jobs.storage_key, already named correctly — no rename needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(dashboard)/[portSlug]/admin/page.tsx

@@ -180,6 +180,13 @@ const GROUPS: AdminGroup[] = [
         description: 'Database snapshots and on-demand exports.',
         icon: HardDrive,
       },
+      {
+        href: 'storage',
+        label: 'Storage Backend',
+        description:
+          'Choose between S3-compatible object store or local filesystem; migrate between them.',
+        icon: HardDrive,
+      },
     ],
   },
   {

src/app/(dashboard)/[portSlug]/admin/storage/page.tsx

@@ -0,0 +1,7 @@
+import { StorageAdminPanel } from '@/components/admin/storage-admin-panel';
+
+export const dynamic = 'force-dynamic';
+
+export default function StorageAdminPage() {
+  return <StorageAdminPanel />;
+}

src/app/api/storage/[token]/route.ts

@@ -0,0 +1,106 @@
+/**
+ * Filesystem-backend download proxy.
+ *
+ * The `FilesystemBackend.presignDownload(...)` returns a CRM-internal URL of
+ * the form `/api/storage/<hmac-signed-token>`. This route verifies the HMAC,
+ * checks expiry, enforces single-use via a short Redis cache, then streams
+ * the file out with explicit `Content-Type` + `Content-Disposition`.
+ *
+ * §14.9a mitigations exercised here:
+ * - HMAC verification (timingSafeEqual via filesystem.verifyProxyToken)
+ * - expiry check (token includes `e` epoch seconds)
+ * - single-use replay protection via short Redis SET-NX
+ * - Node runtime only (no edge); explicit headers so Next.js doesn't try to
+ *   process the bytes (no image optimization, no streaming transforms)
+ */
+
+import { createReadStream } from 'node:fs';
+import * as fs from 'node:fs/promises';
+import { Readable } from 'node:stream';
+
+import { NextRequest, NextResponse } from 'next/server';
+
+import { logger } from '@/lib/logger';
+import { redis } from '@/lib/redis';
+import { FilesystemBackend, getStorageBackend } from '@/lib/storage';
+import { verifyProxyToken } from '@/lib/storage/filesystem';
+
+export const runtime = 'nodejs';
+export const dynamic = 'force-dynamic';
+
+const REPLAY_TTL_SECONDS = 60 * 30; // 30min — longer than any presign expiry default.
+
+export async function GET(
+  _req: NextRequest,
+  ctx: { params: Promise<{ token: string }> },
+): Promise<NextResponse> {
+  const { token } = await ctx.params;
+
+  const backend = await getStorageBackend();
+  if (!(backend instanceof FilesystemBackend)) {
+    return NextResponse.json(
+      { error: 'Storage proxy is only available in filesystem mode' },
+      { status: 404 },
+    );
+  }
+
+  const result = verifyProxyToken(token, backend.getHmacSecret());
+  if (!result.ok) {
+    logger.warn({ reason: result.reason }, 'Storage proxy token rejected');
+    return NextResponse.json({ error: 'Invalid or expired token' }, { status: 403 });
+  }
+  const { payload } = result;
+
+  // Single-use enforcement. SET NX with a TTL longer than the token itself.
+  // Using the body half of the token as the dedup key (signature included
+  // would also work but body is enough — a reused token has the same body).
+  const replayKey = `storage:proxy:seen:${token.split('.')[0]}`;
+  const setOk = await redis.set(replayKey, '1', 'EX', REPLAY_TTL_SECONDS, 'NX');
+  if (setOk !== 'OK') {
+    logger.warn({ key: payload.k }, 'Storage proxy token replay rejected');
+    return NextResponse.json({ error: 'Token already used' }, { status: 403 });
+  }
+
+  let absolutePath: string;
+  try {
+    absolutePath = backend.resolveKeyForProxy(payload.k);
+  } catch (err) {
+    logger.warn({ err, key: payload.k }, 'Storage proxy key resolution failed');
+    return NextResponse.json({ error: 'Invalid key' }, { status: 400 });
+  }
+
+  let size: number;
+  try {
+    const stat = await fs.stat(absolutePath);
+    if (!stat.isFile()) {
+      return NextResponse.json({ error: 'Not found' }, { status: 404 });
+    }
+    size = stat.size;
+  } catch (err) {
+    const code = (err as NodeJS.ErrnoException).code;
+    if (code === 'ENOENT') {
+      return NextResponse.json({ error: 'Not found' }, { status: 404 });
+    }
+    throw err;
+  }
+
+  // Convert the Node Readable into a Web ReadableStream for NextResponse.
+  const nodeStream = createReadStream(absolutePath);
+  const webStream = Readable.toWeb(nodeStream) as unknown as ReadableStream<Uint8Array>;
+
+  const headers = new Headers();
+  headers.set('Content-Type', payload.c ?? 'application/octet-stream');
+  headers.set('Content-Length', String(size));
+  if (payload.f) {
+    // RFC 5987 — quote the filename and provide a UTF-8 fallback.
+    const safe = payload.f.replace(/"/g, '');
+    headers.set(
+      'Content-Disposition',
+      `attachment; filename="${safe}"; filename*=UTF-8''${encodeURIComponent(payload.f)}`,
+    );
+  }
+  headers.set('Cache-Control', 'private, no-store');
+  headers.set('X-Content-Type-Options', 'nosniff');
+
+  return new NextResponse(webStream, { status: 200, headers });
+}

src/app/api/v1/admin/storage/migrate/route.ts

@@ -0,0 +1,40 @@
+/**
+ * Admin-triggered storage migration. Same code path as `scripts/migrate-storage.ts`
+ * (both delegate to `runMigration()` in `@/lib/storage/migrate`). Body:
+ *   { from: 's3'|'filesystem', to: 's3'|'filesystem', dryRun?: boolean }
+ *
+ * Super-admin only. The `/[portSlug]/admin` segment is already gated; this
+ * route enforces the same constraint defensively.
+ */
+
+import { NextResponse } from 'next/server';
+import { z } from 'zod';
+
+import { withAuth } from '@/lib/api/helpers';
+import { parseBody } from '@/lib/api/route-helpers';
+import { errorResponse, ForbiddenError } from '@/lib/errors';
+import { runMigration } from '@/lib/storage/migrate';
+
+const schema = z.object({
+  from: z.enum(['s3', 'filesystem']),
+  to: z.enum(['s3', 'filesystem']),
+  dryRun: z.boolean().default(false),
+});
+
+export const runtime = 'nodejs';
+
+export const POST = withAuth(async (req, ctx) => {
+  try {
+    if (!ctx.isSuperAdmin) {
+      throw new ForbiddenError('Super admin only');
+    }
+    const body = await parseBody(req, schema);
+    if (body.from === body.to) {
+      return NextResponse.json({ error: 'from and to must differ' }, { status: 400 });
+    }
+    const result = await runMigration({ ...body, userId: ctx.userId });
+    return NextResponse.json({ data: result });
+  } catch (error) {
+    return errorResponse(error);
+  }
+});

src/app/api/v1/admin/storage/route.ts

@@ -0,0 +1,72 @@
+/**
+ * Admin storage status + connection test. Super-admin only.
+ *
+ *   GET  /api/v1/admin/storage           — current backend + capacity stats
+ *   POST /api/v1/admin/storage/test      — exercise list/put/get/delete on s3
+ */
+
+import { NextResponse } from 'next/server';
+
+import { withAuth } from '@/lib/api/helpers';
+import { errorResponse, ForbiddenError } from '@/lib/errors';
+import { TABLES_WITH_STORAGE_KEYS } from '@/lib/storage/migrate';
+import { getStorageBackend } from '@/lib/storage';
+import { S3Backend } from '@/lib/storage/s3';
+import { db } from '@/lib/db';
+import { sql } from 'drizzle-orm';
+
+export const runtime = 'nodejs';
+
+export const GET = withAuth(async (_req, ctx) => {
+  try {
+    if (!ctx.isSuperAdmin) {
+      throw new ForbiddenError('Super admin only');
+    }
+    const backend = await getStorageBackend();
+
+    // Aggregate row count + total bytes across every storage-bearing table.
+    let fileCount = 0;
+    const totalBytes = 0;
+    for (const tbl of TABLES_WITH_STORAGE_KEYS) {
+      const result = await db.execute(
+        sql.raw(
+          `SELECT COUNT(*)::bigint AS n FROM ${tbl.table} WHERE ${tbl.keyColumn} IS NOT NULL`,
+        ),
+      );
+      const rows = (
+        Array.isArray(result) ? result : ((result as { rows?: unknown[] }).rows ?? [])
+      ) as Array<{ n: number | string }>;
+      fileCount += Number(rows[0]?.n ?? 0);
+    }
+
+    return NextResponse.json({
+      data: {
+        backend: backend.name,
+        fileCount,
+        totalBytes,
+        tablesTracked: TABLES_WITH_STORAGE_KEYS.map((t) => t.table),
+      },
+    });
+  } catch (error) {
+    return errorResponse(error);
+  }
+});
+
+export const POST = withAuth(async (_req, ctx) => {
+  try {
+    if (!ctx.isSuperAdmin) {
+      throw new ForbiddenError('Super admin only');
+    }
+    const backend = await getStorageBackend();
+    if (!(backend instanceof S3Backend)) {
+      return NextResponse.json(
+        { ok: false, error: 'Test connection only available for S3 backend' },
+        { status: 400 },
+      );
+    }
+    const result = await backend.healthCheck();
+    return NextResponse.json(result);
+  } catch (error) {
+    return errorResponse(error);
+  }
+});

src/components/admin/storage-admin-panel.tsx

@@ -0,0 +1,239 @@
+'use client';
+
+import { useState } from 'react';
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
+import { CheckCircle2, HardDrive, Loader2, RefreshCw, ServerCog, XCircle } from 'lucide-react';
+
+import { PageHeader } from '@/components/shared/page-header';
+import { Button } from '@/components/ui/button';
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import { apiFetch } from '@/lib/api/client';
+
+type BackendName = 's3' | 'filesystem';
+
+interface StorageStatus {
+  backend: BackendName;
+  fileCount: number;
+  totalBytes: number;
+  tablesTracked: string[];
+}
+
+interface MigrationResult {
+  rowsConsidered: number;
+  rowsMigrated: number;
+  rowsSkippedAlreadyDone: number;
+  totalBytes: number;
+  flipped: boolean;
+  dryRun: boolean;
+}
+
+export function StorageAdminPanel() {
+  const queryClient = useQueryClient();
+  const [confirmOpen, setConfirmOpen] = useState(false);
+  const [dryRun, setDryRun] = useState<MigrationResult | null>(null);
+  const [testResult, setTestResult] = useState<{ ok: boolean; error?: string } | null>(null);
+
+  const status = useQuery({
+    queryKey: ['admin', 'storage', 'status'],
+    queryFn: () => apiFetch<{ data: StorageStatus }>('/api/v1/admin/storage'),
+  });
+
+  const dryRunMutation = useMutation({
+    mutationFn: async (opts: { from: BackendName; to: BackendName }) =>
+      apiFetch<{ data: MigrationResult }>('/api/v1/admin/storage/migrate', {
+        method: 'POST',
+        body: JSON.stringify({ ...opts, dryRun: true }),
+      }),
+    onSuccess: (result) => {
+      setDryRun(result.data);
+      setConfirmOpen(true);
+    },
+  });
+
+  const migrateMutation = useMutation({
+    mutationFn: async (opts: { from: BackendName; to: BackendName }) =>
+      apiFetch<{ data: MigrationResult }>('/api/v1/admin/storage/migrate', {
+        method: 'POST',
+        body: JSON.stringify({ ...opts, dryRun: false }),
+      }),
+    onSuccess: () => {
+      setConfirmOpen(false);
+      setDryRun(null);
+      queryClient.invalidateQueries({ queryKey: ['admin', 'storage', 'status'] });
+    },
+  });
+
+  const testMutation = useMutation({
+    mutationFn: async () =>
+      apiFetch<{ ok: boolean; error?: string }>('/api/v1/admin/storage', {
+        method: 'POST',
+      }),
+    onSuccess: (r) => setTestResult(r),
+    onError: (e: Error) => setTestResult({ ok: false, error: e.message }),
+  });
+
+  if (status.isLoading) {
+    return (
+      <div className="flex items-center gap-2 text-sm text-muted-foreground">
+        <Loader2 className="h-4 w-4 animate-spin" /> Loading storage status…
+      </div>
+    );
+  }
+  if (status.isError || !status.data?.data) {
+    return <div className="text-sm text-destructive">Failed to load storage status.</div>;
+  }
+  const s = status.data.data;
+  const otherBackend: BackendName = s.backend === 's3' ? 'filesystem' : 's3';
+
+  return (
+    <div className="space-y-6">
+      <PageHeader
+        title="Storage Backend"
+        description="Where the CRM stores per-berth PDFs, brochures, GDPR exports, and other binary files."
+      />
+
+      <div className="grid gap-4 lg:grid-cols-3">
+        <Card className="lg:col-span-2">
+          <CardHeader className="flex flex-row items-start gap-3 space-y-0 pb-2">
+            {s.backend === 's3' ? (
+              <ServerCog className="mt-0.5 h-5 w-5 text-muted-foreground" />
+            ) : (
+              <HardDrive className="mt-0.5 h-5 w-5 text-muted-foreground" />
+            )}
+            <div>
+              <CardTitle className="text-base">Active backend: {s.backend}</CardTitle>
+              <CardDescription>
+                {s.backend === 's3'
+                  ? 'Files stored in an S3-compatible object store (MinIO, AWS S3, Backblaze B2, Cloudflare R2, Wasabi, Tigris).'
+                  : 'Files stored on the local filesystem under storage_filesystem_root. Single-node deployments only.'}
+              </CardDescription>
+            </div>
+          </CardHeader>
+          <CardContent className="space-y-4">
+            <dl className="grid grid-cols-2 gap-3 text-sm">
+              <div>
+                <dt className="text-muted-foreground">Tracked tables</dt>
+                <dd>
+                  {s.tablesTracked.length === 0
+                    ? '(none yet — Phase 6b)'
+                    : s.tablesTracked.join(', ')}
+                </dd>
+              </div>
+              <div>
+                <dt className="text-muted-foreground">File count</dt>
+                <dd>{s.fileCount}</dd>
+              </div>
+            </dl>
+
+            <div className="flex flex-wrap gap-3">
+              <Button
+                variant="outline"
+                disabled={dryRunMutation.isPending}
+                onClick={() => dryRunMutation.mutate({ from: s.backend, to: otherBackend })}
+              >
+                {dryRunMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
+                Switch to {otherBackend}
+              </Button>
+              {s.backend === 's3' && (
+                <Button
+                  variant="outline"
+                  onClick={() => testMutation.mutate()}
+                  disabled={testMutation.isPending}
+                >
+                  {testMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
+                  Test connection
+                </Button>
+              )}
+              <Button variant="ghost" onClick={() => status.refetch()} disabled={status.isFetching}>
+                <RefreshCw className="mr-2 h-4 w-4" /> Refresh
+              </Button>
+            </div>
+
+            {testResult && (
+              <div className="rounded-md border p-3 text-sm">
+                {testResult.ok ? (
+                  <div className="flex items-center gap-2 text-emerald-600">
+                    <CheckCircle2 className="h-4 w-4" /> Connection OK — round-trip succeeded.
+                  </div>
+                ) : (
+                  <div className="flex items-center gap-2 text-destructive">
+                    <XCircle className="h-4 w-4" /> {testResult.error ?? 'Connection failed'}
+                  </div>
+                )}
+              </div>
+            )}
+          </CardContent>
+        </Card>
+
+        <Card>
+          <CardHeader>
+            <CardTitle className="text-base">Backup notes</CardTitle>
+          </CardHeader>
+          <CardContent className="space-y-2 text-sm text-muted-foreground">
+            {s.backend === 's3' ? (
+              <p>
+                S3 mode: configure your provider&apos;s lifecycle / replication / versioning
+                policies as your primary backup. The CRM does not duplicate object storage in its
+                own backups.
+              </p>
+            ) : (
+              <p>
+                Filesystem mode: include the storage root directory in your backup tool (restic,
+                borg, snapshots). It sits next to the database; the two should be backed up
+                together.
+              </p>
+            )}
+            <p className="pt-2 text-xs">
+              Filesystem mode refuses to start when MULTI_NODE_DEPLOYMENT=true. For multi-node
+              deployments, switch to an S3-compatible backend.
+            </p>
+          </CardContent>
+        </Card>
+      </div>
+
+      <Dialog open={confirmOpen} onOpenChange={setConfirmOpen}>
+        <DialogContent>
+          <DialogHeader>
+            <DialogTitle>Switch storage backend</DialogTitle>
+            <DialogDescription>
+              Move all tracked files from the current backend to the new backend, verify each file
+              via sha256, then atomically flip the active backend.
+            </DialogDescription>
+          </DialogHeader>
+          {dryRun && (
+            <div className="rounded-md border p-3 text-sm">
+              <dl className="grid grid-cols-2 gap-2">
+                <dt className="text-muted-foreground">Rows considered</dt>
+                <dd>{dryRun.rowsConsidered}</dd>
+                <dt className="text-muted-foreground">Already migrated (resumable)</dt>
+                <dd>{dryRun.rowsSkippedAlreadyDone}</dd>
+                <dt className="text-muted-foreground">Total bytes</dt>
+                <dd>{Math.round(dryRun.totalBytes / 1024)} KB</dd>
+              </dl>
+            </div>
+          )}
+          <DialogFooter>
+            <Button variant="outline" onClick={() => setConfirmOpen(false)}>
+              Cancel
+            </Button>
+            <Button
+              disabled={migrateMutation.isPending}
+              onClick={() => migrateMutation.mutate({ from: s.backend, to: otherBackend })}
+            >
+              {migrateMutation.isPending && <Loader2 className="mr-2 h-4 w-4 animate-spin" />}
+              Migrate now
+            </Button>
+          </DialogFooter>
+        </DialogContent>
+      </Dialog>
+    </div>
+  );
+}

src/lib/storage/filesystem.ts

@@ -0,0 +1,345 @@
+/**
+ * Local filesystem backend. Stores files at `${root}/<key>` on disk and serves
+ * downloads via a CRM-internal proxy route (`/api/storage/[token]`) that
+ * verifies an HMAC token before streaming the bytes. Used for single-VPS
+ * deployments where running MinIO is overkill.
+ *
+ * §14.9a critical mitigations:
+ *
+ * - Storage keys are validated against `^[a-zA-Z0-9/_.-]+$`. Anything containing
+ *   `..` or that resolves to an absolute path is rejected.
+ * - The resolved path is checked with `path.resolve` against the resolved
+ *   storage root (realpath form) — symlink escapes are blocked.
+ * - The storage root is created with mode `0o700` (owner only).
+ * - Refuses to start when `MULTI_NODE_DEPLOYMENT === 'true'` — multi-node
+ *   deployments must use an S3-compatible store.
+ * - Proxy download URLs carry an HMAC-signed payload (key + expiry); the
+ *   route refuses to stream a key whose token doesn't verify.
+ */
+
+import { createHash, createHmac, randomUUID, timingSafeEqual } from 'node:crypto';
+import { createReadStream } from 'node:fs';
+import * as fs from 'node:fs/promises';
+import * as path from 'node:path';
+import { Readable } from 'node:stream';
+
+import { env } from '@/lib/env';
+import { NotFoundError, ValidationError } from '@/lib/errors';
+import { logger } from '@/lib/logger';
+import { decrypt } from '@/lib/utils/encryption';
+
+import type { PresignOpts, PutOpts, StorageBackend } from './index';
+
+// ─── key validation ─────────────────────────────────────────────────────────
+
+const VALID_KEY_RE = /^[a-zA-Z0-9/_.-]+$/;
+
+/**
+ * Validate a storage key. Rejects:
+ * - empty / whitespace
+ * - characters outside `[a-zA-Z0-9/_.-]`
+ * - traversal segments (`..`, `/..`, `../`)
+ * - absolute paths (leading `/`)
+ * - segments starting with `.` (hidden files / dotfiles other than the
+ *   intentional dot-extension at the end)
+ *
+ * Use this both at write time AND at read time — a key fed back from the DB
+ * could in theory have been tampered with at rest.
+ */
+export function validateStorageKey(key: string): void {
+  if (typeof key !== 'string' || key.length === 0) {
+    throw new ValidationError('Storage key must be a non-empty string');
+  }
+  if (key.length > 1024) {
+    throw new ValidationError('Storage key exceeds 1024 chars');
+  }
+  if (key.startsWith('/') || key.startsWith('\\')) {
+    throw new ValidationError('Storage key must not be absolute');
+  }
+  if (!VALID_KEY_RE.test(key)) {
+    throw new ValidationError('Storage key contains forbidden characters');
+  }
+  // Reject any traversal segment in any normalized form.
+  const segments = key.split('/');
+  for (const seg of segments) {
+    if (seg === '..' || seg === '.' || seg === '') {
+      throw new ValidationError('Storage key has empty or traversal segment');
+    }
+  }
+}
+
+// ─── HMAC token helpers ─────────────────────────────────────────────────────
+
+interface ProxyTokenPayload {
+  /** Storage key (validated). */
+  k: string;
+  /** Expiry epoch seconds. */
+  e: number;
+  /** Random nonce so two URLs for the same (key, expiry) differ. */
+  n: string;
+  /** Optional download filename. */
+  f?: string;
+  /** Optional content-type override. */
+  c?: string;
+}
+
+function b64urlEncode(buf: Buffer): string {
+  return buf.toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
+}
+
+function b64urlDecode(s: string): Buffer {
+  const pad = s.length % 4 === 0 ? '' : '='.repeat(4 - (s.length % 4));
+  return Buffer.from(s.replace(/-/g, '+').replace(/_/g, '/') + pad, 'base64');
+}
+
+export function signProxyToken(payload: ProxyTokenPayload, secret: string): string {
+  const json = JSON.stringify(payload);
+  const body = b64urlEncode(Buffer.from(json, 'utf8'));
+  const sig = createHmac('sha256', secret).update(body).digest();
+  return `${body}.${b64urlEncode(sig)}`;
+}
+
+export function verifyProxyToken(
+  token: string,
+  secret: string,
+): { ok: true; payload: ProxyTokenPayload } | { ok: false; reason: string } {
+  if (typeof token !== 'string' || !token.includes('.')) {
+    return { ok: false, reason: 'malformed' };
+  }
+  const [body, sigB64] = token.split('.', 2);
+  if (!body || !sigB64) return { ok: false, reason: 'malformed' };
+
+  const expected = createHmac('sha256', secret).update(body).digest();
+  let provided: Buffer;
+  try {
+    provided = b64urlDecode(sigB64);
+  } catch {
+    return { ok: false, reason: 'malformed' };
+  }
+  if (provided.length !== expected.length) return { ok: false, reason: 'sig-mismatch' };
+  if (!timingSafeEqual(provided, expected)) return { ok: false, reason: 'sig-mismatch' };
+
+  let payload: ProxyTokenPayload;
+  try {
+    payload = JSON.parse(b64urlDecode(body).toString('utf8')) as ProxyTokenPayload;
+  } catch {
+    return { ok: false, reason: 'malformed-payload' };
+  }
+
+  if (typeof payload.e !== 'number' || payload.e * 1000 < Date.now()) {
+    return { ok: false, reason: 'expired' };
+  }
+  try {
+    validateStorageKey(payload.k);
+  } catch {
+    return { ok: false, reason: 'invalid-key' };
+  }
+  return { ok: true, payload };
+}
+
+// ─── backend ────────────────────────────────────────────────────────────────
+
+interface FilesystemConfig {
+  root: string;
+  /** AES-GCM-encrypted HMAC secret. When absent, falls back to a derived secret. */
+  proxyHmacSecretEncrypted: string | null;
+}
+
+export class FilesystemBackend implements StorageBackend {
+  readonly name = 'filesystem' as const;
+
+  private rootResolved: string;
+  private hmacSecret: string;
+
+  private constructor(rootResolved: string, hmacSecret: string) {
+    this.rootResolved = rootResolved;
+    this.hmacSecret = hmacSecret;
+  }
+
+  /** Throws if multi-node mode is set or the root isn't writable. */
+  static async create(cfg: FilesystemConfig): Promise<FilesystemBackend> {
+    if (process.env.MULTI_NODE_DEPLOYMENT === 'true') {
+      throw new Error(
+        'FilesystemBackend cannot start when MULTI_NODE_DEPLOYMENT=true. ' +
+          'Use an S3-compatible backend for multi-node deployments.',
+      );
+    }
+    const rootInput = cfg.root || './storage';
+    const rootAbs = path.isAbsolute(rootInput) ? rootInput : path.resolve(process.cwd(), rootInput);
+    await fs.mkdir(rootAbs, { recursive: true, mode: 0o700 });
+    // Defensive: re-chmod even if it already existed.
+    await fs.chmod(rootAbs, 0o700).catch(() => undefined);
+    // Use realpath so symlinked roots are flattened to their actual location;
+    // we then compare every per-key resolution against this exact prefix.
+    const rootResolved = await fs.realpath(rootAbs);
+
+    const hmacSecret = resolveHmacSecret(cfg.proxyHmacSecretEncrypted);
+    logger.info({ root: rootResolved }, 'FilesystemBackend ready');
+    return new FilesystemBackend(rootResolved, hmacSecret);
+  }
+
+  /**
+   * Resolve a (validated) storage key to an absolute path under the root.
+   * Throws if the resolved path escapes the storage root via symlink/.. tricks.
+   */
+  private resolveKey(key: string): string {
+    validateStorageKey(key);
+    const joined = path.join(this.rootResolved, key);
+    const resolved = path.resolve(joined);
+    if (resolved !== this.rootResolved && !resolved.startsWith(this.rootResolved + path.sep)) {
+      throw new ValidationError('Storage key escapes storage root');
+    }
+    return resolved;
+  }
+
+  async put(
+    key: string,
+    body: Buffer | NodeJS.ReadableStream,
+    opts: PutOpts,
+  ): Promise<{ key: string; sizeBytes: number; sha256: string }> {
+    const target = this.resolveKey(key);
+    await fs.mkdir(path.dirname(target), { recursive: true, mode: 0o700 });
+
+    const buffer = Buffer.isBuffer(body) ? body : await streamToBuffer(body);
+    const sha256 = opts.sha256 ?? createHash('sha256').update(buffer).digest('hex');
+
+    // Atomic write via temp + rename so partial writes don't leave half-files.
+    const tmp = `${target}.${randomUUID()}.tmp`;
+    await fs.writeFile(tmp, buffer, { mode: 0o600 });
+    // realpath the temp to make sure the final-rename target resolves correctly
+    // even if some segment of the path is a symlink we just created.
+    await fs.rename(tmp, target);
+
+    return { key, sizeBytes: buffer.length, sha256 };
+  }
+
+  async get(key: string): Promise<NodeJS.ReadableStream> {
+    const target = this.resolveKey(key);
+    try {
+      const stat = await fs.stat(target);
+      if (!stat.isFile()) throw new NotFoundError(`Storage object ${key}`);
+    } catch (err) {
+      const code = (err as NodeJS.ErrnoException).code;
+      if (code === 'ENOENT') throw new NotFoundError(`Storage object ${key}`);
+      throw err;
+    }
+    return createReadStream(target);
+  }
+
+  async head(key: string): Promise<{ sizeBytes: number; contentType: string } | null> {
+    const target = this.resolveKey(key);
+    try {
+      const stat = await fs.stat(target);
+      if (!stat.isFile()) return null;
+      // Filesystem doesn't track content-type. Caller should consult the DB
+      // (or sniff via ext) — we return application/octet-stream as a default.
+      return { sizeBytes: stat.size, contentType: extToContentType(target) };
+    } catch (err) {
+      const code = (err as NodeJS.ErrnoException).code;
+      if (code === 'ENOENT') return null;
+      throw err;
+    }
+  }
+
+  async delete(key: string): Promise<void> {
+    const target = this.resolveKey(key);
+    try {
+      await fs.unlink(target);
+    } catch (err) {
+      const code = (err as NodeJS.ErrnoException).code;
+      if (code === 'ENOENT') return;
+      throw err;
+    }
+  }
+
+  /**
+   * Filesystem mode never exposes a direct upload URL. The CRM-internal proxy
+   * accepts uploads via the regular API surface (multipart POST to /api/v1/...
+   * or PUT to /api/storage/[token]). We return a placeholder PUT URL pointing
+   * at the proxy so the contract stays uniform.
+   */
+  async presignUpload(
+    key: string,
+    opts: PresignOpts,
+  ): Promise<{ url: string; method: 'PUT' | 'POST' }> {
+    validateStorageKey(key);
+    const expiresAt = Math.floor(Date.now() / 1000) + (opts.expirySeconds ?? 900);
+    const token = signProxyToken(
+      { k: key, e: expiresAt, n: randomUUID(), c: opts.contentType },
+      this.hmacSecret,
+    );
+    return { url: `/api/storage/${token}`, method: 'PUT' };
+  }
+
+  async presignDownload(key: string, opts: PresignOpts): Promise<{ url: string; expiresAt: Date }> {
+    validateStorageKey(key);
+    const expirySec = opts.expirySeconds ?? 900;
+    const expiresAtSec = Math.floor(Date.now() / 1000) + expirySec;
+    const token = signProxyToken(
+      { k: key, e: expiresAtSec, n: randomUUID(), f: opts.filename, c: opts.contentType },
+      this.hmacSecret,
+    );
+    return {
+      url: `/api/storage/${token}`,
+      expiresAt: new Date(expiresAtSec * 1000),
+    };
+  }
+
+  /** Used by the proxy route — returns the validated absolute path. */
+  resolveKeyForProxy(key: string): string {
+    return this.resolveKey(key);
+  }
+
+  /** Used by the proxy route — same HMAC secret as presignDownload. */
+  getHmacSecret(): string {
+    return this.hmacSecret;
+  }
+}
+
+// ─── helpers ────────────────────────────────────────────────────────────────
+
+function resolveHmacSecret(encryptedSecret: string | null): string {
+  if (encryptedSecret) {
+    try {
+      return decrypt(encryptedSecret);
+    } catch (err) {
+      logger.error({ err }, 'Failed to decrypt storage_proxy_hmac_secret_encrypted');
+    }
+  }
+  // Derive a stable per-process secret from BETTER_AUTH_SECRET so dev mode
+  // works without explicit configuration. In production the admin UI writes
+  // an encrypted random secret.
+  const seed = process.env.BETTER_AUTH_SECRET ?? env.BETTER_AUTH_SECRET ?? 'storage-default';
+  return createHash('sha256').update(`storage-proxy:${seed}`).digest('hex');
+}
+
+async function streamToBuffer(stream: NodeJS.ReadableStream): Promise<Buffer> {
+  const chunks: Buffer[] = [];
+  for await (const chunk of stream as Readable) {
+    chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string));
+  }
+  return Buffer.concat(chunks);
+}
+
+function extToContentType(filename: string): string {
+  const ext = path.extname(filename).toLowerCase();
+  switch (ext) {
+    case '.pdf':
+      return 'application/pdf';
+    case '.png':
+      return 'image/png';
+    case '.jpg':
+    case '.jpeg':
+      return 'image/jpeg';
+    case '.json':
+      return 'application/json';
+    case '.txt':
+      return 'text/plain';
+    case '.csv':
+      return 'text/csv';
+    case '.zip':
+      return 'application/zip';
+    default:
+      return 'application/octet-stream';
+  }
+}

src/lib/storage/index.ts

@@ -0,0 +1,200 @@
+/**
+ * Pluggable storage backend (Phase 6a — see docs/berth-recommender-and-pdf-plan.md §4.7a).
+ *
+ * The CRM stores files (per-berth PDFs, brochures, GDPR exports, etc.) through a
+ * single `StorageBackend` abstraction. The deployment chooses between an
+ * S3-compatible store (MinIO / AWS S3 / Backblaze B2 / Cloudflare R2 / Wasabi /
+ * Tigris) and a local filesystem at runtime via `system_settings.storage_backend`.
+ *
+ * Callers should always import from this barrel — never from `s3.ts` or
+ * `filesystem.ts` directly — so the factory wiring stays the single source of
+ * truth.
+ */
+
+import { and, eq, isNull } from 'drizzle-orm';
+
+import { db } from '@/lib/db';
+import { systemSettings } from '@/lib/db/schema/system';
+import { logger } from '@/lib/logger';
+
+import { FilesystemBackend } from './filesystem';
+import { S3Backend } from './s3';
+
+export type StorageBackendName = 's3' | 'filesystem';
+
+export interface PutOpts {
+  contentType: string;
+  /** Optional pre-computed sha256 hex — if absent, the backend computes one. */
+  sha256?: string;
+  /** Bytes (for streams that don't expose .length); used for capacity pre-flight. */
+  sizeBytes?: number;
+  /** Optional content-disposition for downloads (filesystem proxy only). */
+  contentDisposition?: string;
+}
+
+export interface PresignOpts {
+  /** TTL in seconds. Default 900 (15min) per SECURITY-GUIDELINES §7.1. */
+  expirySeconds?: number;
+  contentType?: string;
+  /** Filename used in Content-Disposition for downloads. */
+  filename?: string;
+}
+
+export interface StorageBackend {
+  /** Upload bytes. Returns the canonical key, size, and sha256 hex. */
+  put(
+    key: string,
+    body: Buffer | NodeJS.ReadableStream,
+    opts: PutOpts,
+  ): Promise<{ key: string; sizeBytes: number; sha256: string }>;
+
+  /** Stream a file out. Throws NotFoundError if missing. */
+  get(key: string): Promise<NodeJS.ReadableStream>;
+
+  /** Existence + size check without reading the full body. Returns null when missing. */
+  head(key: string): Promise<{ sizeBytes: number; contentType: string } | null>;
+
+  /** Delete. Idempotent — missing keys must not throw. */
+  delete(key: string): Promise<void>;
+
+  /** Generate a short-lived URL the browser can PUT to. */
+  presignUpload(key: string, opts: PresignOpts): Promise<{ url: string; method: 'PUT' | 'POST' }>;
+
+  /** Generate a short-lived URL the browser can GET from. */
+  presignDownload(key: string, opts: PresignOpts): Promise<{ url: string; expiresAt: Date }>;
+
+  readonly name: StorageBackendName;
+}
+
+// ─── factory ────────────────────────────────────────────────────────────────
+
+interface CachedFactory {
+  backend: StorageBackend;
+  /** Resolved at cache-time so we can re-fetch when settings change. */
+  configFingerprint: string;
+}
+
+let cached: CachedFactory | null = null;
+
+/**
+ * Reset the per-process backend cache. Called after `system_settings` writes
+ * via the existing pub/sub invalidation hook, and exposed for tests.
+ */
+export function resetStorageBackendCache(): void {
+  cached = null;
+}
+
+interface StorageConfigSnapshot {
+  backend: StorageBackendName;
+  s3?: {
+    endpoint?: string;
+    region?: string;
+    bucket?: string;
+    accessKey?: string;
+    secretKeyEncrypted?: string;
+    forcePathStyle?: boolean;
+  };
+  filesystem?: {
+    root?: string;
+    proxyHmacSecretEncrypted?: string;
+  };
+}
+
+async function readGlobalSetting<T = unknown>(key: string): Promise<T | null> {
+  const [row] = await db
+    .select()
+    .from(systemSettings)
+    .where(and(eq(systemSettings.key, key), isNull(systemSettings.portId)));
+  return (row?.value as T | undefined) ?? null;
+}
+
+async function loadStorageConfig(): Promise<StorageConfigSnapshot> {
+  // Each setting key is a separate row. We read them in parallel.
+  const keys = [
+    'storage_backend',
+    'storage_s3_endpoint',
+    'storage_s3_region',
+    'storage_s3_bucket',
+    'storage_s3_access_key',
+    'storage_s3_secret_key_encrypted',
+    'storage_s3_force_path_style',
+    'storage_filesystem_root',
+    'storage_proxy_hmac_secret_encrypted',
+  ] as const;
+  const [
+    backendRaw,
+    s3Endpoint,
+    s3Region,
+    s3Bucket,
+    s3AccessKey,
+    s3SecretKeyEncrypted,
+    s3ForcePathStyle,
+    fsRoot,
+    fsHmacSecretEncrypted,
+  ] = await Promise.all(keys.map((k) => readGlobalSetting<unknown>(k)));
+
+  const backend: StorageBackendName = backendRaw === 'filesystem' ? 'filesystem' : 's3';
+
+  return {
+    backend,
+    s3: {
+      endpoint: typeof s3Endpoint === 'string' ? s3Endpoint : undefined,
+      region: typeof s3Region === 'string' ? s3Region : undefined,
+      bucket: typeof s3Bucket === 'string' ? s3Bucket : undefined,
+      accessKey: typeof s3AccessKey === 'string' ? s3AccessKey : undefined,
+      secretKeyEncrypted:
+        typeof s3SecretKeyEncrypted === 'string' ? s3SecretKeyEncrypted : undefined,
+      forcePathStyle:
+        typeof s3ForcePathStyle === 'boolean' ? s3ForcePathStyle : Boolean(s3ForcePathStyle),
+    },
+    filesystem: {
+      root: typeof fsRoot === 'string' ? fsRoot : undefined,
+      proxyHmacSecretEncrypted:
+        typeof fsHmacSecretEncrypted === 'string' ? fsHmacSecretEncrypted : undefined,
+    },
+  };
+}
+
+function fingerprint(cfg: StorageConfigSnapshot): string {
+  return JSON.stringify(cfg);
+}
+
+/**
+ * Resolve the active backend. Caches per-process; the cache is invalidated by
+ * `resetStorageBackendCache()` (called when `system_settings.storage_backend`
+ * changes via the migration flow).
+ */
+export async function getStorageBackend(): Promise<StorageBackend> {
+  const cfg = await loadStorageConfig();
+  const fp = fingerprint(cfg);
+  if (cached && cached.configFingerprint === fp) {
+    return cached.backend;
+  }
+
+  const backend = await buildBackend(cfg);
+  cached = { backend, configFingerprint: fp };
+  logger.info({ backend: backend.name }, 'Storage backend resolved');
+  return backend;
+}
+
+async function buildBackend(cfg: StorageConfigSnapshot): Promise<StorageBackend> {
+  if (cfg.backend === 'filesystem') {
+    return FilesystemBackend.create({
+      root: cfg.filesystem?.root ?? './storage',
+      proxyHmacSecretEncrypted: cfg.filesystem?.proxyHmacSecretEncrypted ?? null,
+    });
+  }
+  return S3Backend.create({
+    endpoint: cfg.s3?.endpoint,
+    region: cfg.s3?.region,
+    bucket: cfg.s3?.bucket,
+    accessKey: cfg.s3?.accessKey,
+    secretKeyEncrypted: cfg.s3?.secretKeyEncrypted,
+    forcePathStyle: cfg.s3?.forcePathStyle,
+  });
+}
+
+// ─── re-exports ─────────────────────────────────────────────────────────────
+
+export { S3Backend } from './s3';
+export { FilesystemBackend, validateStorageKey } from './filesystem';

src/lib/storage/migrate.ts

@@ -0,0 +1,318 @@
+/**
+ * Storage backend migration core. The CLI in `scripts/migrate-storage.ts` and
+ * the admin API at `/api/v1/admin/storage/migrate` both call `runMigration()`
+ * here, so behaviour is identical regardless of trigger.
+ *
+ * See docs/berth-recommender-and-pdf-plan.md §4.7a + §14.9a for the contract.
+ */
+
+import { createHash } from 'node:crypto';
+import { statfs } from 'node:fs/promises';
+import { Readable } from 'node:stream';
+
+import { and, eq, isNull, sql } from 'drizzle-orm';
+
+import { db } from '@/lib/db';
+import { systemSettings } from '@/lib/db/schema/system';
+
+import { FilesystemBackend } from './filesystem';
+import { resetStorageBackendCache, type StorageBackend, type StorageBackendName } from './index';
+import { S3Backend } from './s3';
+
+// ─── tables to walk ─────────────────────────────────────────────────────────
+
+export interface StorageKeyTable {
+  table: string;
+  /** Column name holding the storage key (always `storage_key` going forward). */
+  keyColumn: string;
+  /** Primary-key column for per-row progress markers. */
+  pkColumn: string;
+  /** Optional content-type column (lets the target backend persist Content-Type). */
+  contentTypeColumn?: string;
+}
+
+/**
+ * Phase 6a ships an empty list — `berth_pdf_versions` and `brochure_versions`
+ * land in Phase 6b. Add new entries here when new file-bearing tables are
+ * introduced. The migration script reads each named table via raw SQL so it
+ * does not need to import every domain's Drizzle schema.
+ */
+export const TABLES_WITH_STORAGE_KEYS: StorageKeyTable[] = [
+  // { table: 'berth_pdf_versions', keyColumn: 'storage_key', pkColumn: 'id', contentTypeColumn: 'content_type' },
+  // { table: 'brochure_versions',  keyColumn: 'storage_key', pkColumn: 'id', contentTypeColumn: 'content_type' },
+];
+
+const ADVISORY_LOCK_KEY = 0xc7000a01;
+
+// ─── helpers ────────────────────────────────────────────────────────────────
+
+interface CliArgs {
+  from: StorageBackendName;
+  to: StorageBackendName;
+  dryRun: boolean;
+}
+
+export function parseArgs(argv: string[]): CliArgs {
+  const args: Partial<CliArgs> = { dryRun: false };
+  for (let i = 0; i < argv.length; i++) {
+    const a = argv[i];
+    if (a === '--dry-run') args.dryRun = true;
+    else if (a === '--from') args.from = argv[++i] as StorageBackendName;
+    else if (a === '--to') args.to = argv[++i] as StorageBackendName;
+  }
+  if (!args.from || !args.to || (args.from !== 's3' && args.from !== 'filesystem')) {
+    throw new Error('Usage: --from s3|filesystem --to s3|filesystem [--dry-run]');
+  }
+  if (args.to !== 's3' && args.to !== 'filesystem') {
+    throw new Error('--to must be s3 or filesystem');
+  }
+  if (args.from === args.to) {
+    throw new Error('--from and --to must differ');
+  }
+  return args as CliArgs;
+}
+
+async function ensureProgressTable(): Promise<void> {
+  await db.execute(sql`
+    CREATE TABLE IF NOT EXISTS _storage_migration_progress (
+      table_name text NOT NULL,
+      row_pk text NOT NULL,
+      storage_key text NOT NULL,
+      sha256 text NOT NULL,
+      size_bytes bigint NOT NULL,
+      migrated_at timestamptz NOT NULL DEFAULT now(),
+      PRIMARY KEY (table_name, row_pk)
+    )
+  `);
+}
+
+function rowsOf(result: unknown): unknown[] {
+  if (Array.isArray(result)) return result;
+  const r = result as { rows?: unknown[] } | null;
+  return r?.rows ?? [];
+}
+
+async function isRowMigrated(tableName: string, pk: string): Promise<boolean> {
+  const res = await db.execute(sql`
+    SELECT 1 FROM _storage_migration_progress
+    WHERE table_name = ${tableName} AND row_pk = ${pk}
+    LIMIT 1
+  `);
+  return rowsOf(res).length > 0;
+}
+
+async function markRowMigrated(
+  tableName: string,
+  pk: string,
+  key: string,
+  sha256: string,
+  sizeBytes: number,
+): Promise<void> {
+  await db.execute(sql`
+    INSERT INTO _storage_migration_progress (table_name, row_pk, storage_key, sha256, size_bytes)
+    VALUES (${tableName}, ${pk}, ${key}, ${sha256}, ${sizeBytes})
+    ON CONFLICT (table_name, row_pk) DO NOTHING
+  `);
+}
+
+interface RowRef {
+  tableName: string;
+  pk: string;
+  key: string;
+  contentType: string;
+}
+
+async function listKeysFor(tbl: StorageKeyTable): Promise<RowRef[]> {
+  const ctSelect = tbl.contentTypeColumn ? `, ${tbl.contentTypeColumn} as content_type` : '';
+  const result = await db.execute(
+    sql.raw(
+      `SELECT ${tbl.pkColumn} as pk, ${tbl.keyColumn} as key${ctSelect}
+       FROM ${tbl.table}
+       WHERE ${tbl.keyColumn} IS NOT NULL`,
+    ),
+  );
+  const rows = rowsOf(result) as Array<{ pk: unknown; key: unknown; content_type?: unknown }>;
+  return rows.map((r) => ({
+    tableName: tbl.table,
+    pk: String(r.pk),
+    key: String(r.key),
+    contentType:
+      typeof r.content_type === 'string' && r.content_type.length > 0
+        ? r.content_type
+        : 'application/octet-stream',
+  }));
+}
+
+// ─── streaming + sha256 verify ──────────────────────────────────────────────
+
+/**
+ * Stream a file from `source` -> `target` while computing sha256 of the bytes
+ * actually written. Re-fetches the target object and verifies a second time
+ * to catch storage-side corruption.
+ */
+export async function copyAndVerify(
+  source: StorageBackend,
+  target: StorageBackend,
+  ref: RowRef,
+): Promise<{ sha256: string; sizeBytes: number }> {
+  const stream = await source.get(ref.key);
+  const chunks: Buffer[] = [];
+  for await (const chunk of stream as Readable) {
+    chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string));
+  }
+  const buffer = Buffer.concat(chunks);
+  const sha256 = createHash('sha256').update(buffer).digest('hex');
+
+  const putResult = await target.put(ref.key, buffer, {
+    contentType: ref.contentType,
+    sha256,
+    sizeBytes: buffer.length,
+  });
+  if (putResult.sha256 !== sha256) {
+    throw new Error(`sha256 mismatch on put for ${ref.tableName}/${ref.pk}`);
+  }
+
+  // Re-fetch from the target and verify a second time.
+  const verifyStream = await target.get(ref.key);
+  const verifyChunks: Buffer[] = [];
+  for await (const chunk of verifyStream as Readable) {
+    verifyChunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string));
+  }
+  const verifyBuf = Buffer.concat(verifyChunks);
+  const verifySha = createHash('sha256').update(verifyBuf).digest('hex');
+  if (verifySha !== sha256) {
+    throw new Error(`sha256 mismatch after round-trip for ${ref.tableName}/${ref.pk} (${ref.key})`);
+  }
+  return { sha256, sizeBytes: buffer.length };
+}
+
+// ─── pre-flight ─────────────────────────────────────────────────────────────
+
+async function freeBytesAt(rootPath: string): Promise<number> {
+  const s = await statfs(rootPath);
+  return Number(s.bavail) * Number(s.bsize);
+}
+
+async function flipBackendSetting(target: StorageBackendName, userId: string): Promise<void> {
+  const existing = await db.query.systemSettings.findFirst({
+    where: and(eq(systemSettings.key, 'storage_backend'), isNull(systemSettings.portId)),
+  });
+  if (existing) {
+    await db
+      .update(systemSettings)
+      .set({ value: target, updatedBy: userId, updatedAt: new Date() })
+      .where(and(eq(systemSettings.key, 'storage_backend'), isNull(systemSettings.portId)));
+  } else {
+    await db.insert(systemSettings).values({
+      key: 'storage_backend',
+      value: target,
+      portId: null,
+      updatedBy: userId,
+    });
+  }
+  resetStorageBackendCache();
+}
+
+// ─── main ───────────────────────────────────────────────────────────────────
+
+export interface MigrationOptions {
+  from: StorageBackendName;
+  to: StorageBackendName;
+  dryRun: boolean;
+  /** Override for tests. */
+  source?: StorageBackend;
+  target?: StorageBackend;
+  /** Audit user id. */
+  userId?: string;
+}
+
+export interface MigrationResult {
+  rowsConsidered: number;
+  rowsMigrated: number;
+  rowsSkippedAlreadyDone: number;
+  totalBytes: number;
+  flipped: boolean;
+  dryRun: boolean;
+}
+
+export async function runMigration(opts: MigrationOptions): Promise<MigrationResult> {
+  const lockResult = await db.execute(sql`SELECT pg_try_advisory_lock(${ADVISORY_LOCK_KEY}) as ok`);
+  const lockRows = rowsOf(lockResult) as Array<{ ok: boolean }>;
+  if (!lockRows[0]?.ok) {
+    throw new Error('Could not acquire storage migration advisory lock');
+  }
+
+  try {
+    await ensureProgressTable();
+
+    const source = opts.source ?? (await buildBackendForMigration(opts.from));
+    const target = opts.target ?? (await buildBackendForMigration(opts.to));
+
+    let rowsConsidered = 0;
+    let rowsMigrated = 0;
+    let rowsSkippedAlreadyDone = 0;
+    let totalBytes = 0;
+
+    for (const tbl of TABLES_WITH_STORAGE_KEYS) {
+      const refs = await listKeysFor(tbl);
+      rowsConsidered += refs.length;
+
+      // Pre-flight free-disk check when target is filesystem.
+      if (opts.to === 'filesystem' && target instanceof FilesystemBackend) {
+        const heads = await Promise.all(
+          refs.map((r) => source.head(r.key).then((h) => h?.sizeBytes ?? 0)),
+        );
+        const sumBytes = heads.reduce((a, b) => a + b, 0);
+        const free = await freeBytesAt(process.cwd());
+        if (free < sumBytes * 1.2) {
+          throw new Error(
+            `Insufficient disk: need ${Math.round(sumBytes / 1e6)}MB + 20% margin, have ${Math.round(free / 1e6)}MB free`,
+          );
+        }
+      }
+
+      for (const ref of refs) {
+        if (await isRowMigrated(ref.tableName, ref.pk)) {
+          rowsSkippedAlreadyDone += 1;
+          continue;
+        }
+        if (opts.dryRun) {
+          const head = await source.head(ref.key);
+          totalBytes += head?.sizeBytes ?? 0;
+          continue;
+        }
+        const { sha256, sizeBytes } = await copyAndVerify(source, target, ref);
+        await markRowMigrated(ref.tableName, ref.pk, ref.key, sha256, sizeBytes);
+        rowsMigrated += 1;
+        totalBytes += sizeBytes;
+      }
+    }
+
+    let flipped = false;
+    if (!opts.dryRun) {
+      await flipBackendSetting(opts.to, opts.userId ?? 'cli:migrate-storage');
+      flipped = true;
+    }
+
+    return {
+      rowsConsidered,
+      rowsMigrated,
+      rowsSkippedAlreadyDone,
+      totalBytes,
+      flipped,
+      dryRun: opts.dryRun,
+    };
+  } finally {
+    await db.execute(sql`SELECT pg_advisory_unlock(${ADVISORY_LOCK_KEY})`);
+  }
+}
+
+async function buildBackendForMigration(name: StorageBackendName): Promise<StorageBackend> {
+  if (name === 'filesystem') {
+    return FilesystemBackend.create({
+      root: process.env.STORAGE_FILESYSTEM_ROOT ?? './storage',
+      proxyHmacSecretEncrypted: null,
+    });
+  }
+  return S3Backend.create({});
+}

src/lib/storage/s3.ts

@@ -0,0 +1,209 @@
+/**
+ * S3-compatible backend (MinIO / AWS S3 / Backblaze B2 / Cloudflare R2 /
+ * Wasabi / Tigris). Wraps the existing `minio` JS client so we keep one
+ * dependency for every S3-shaped service.
+ *
+ * Configuration is sourced from `system_settings` rows (passed in by the
+ * factory in `index.ts`). When system_settings are missing we fall back to
+ * the legacy `MINIO_*` env vars, so an upgrade path doesn't require admins
+ * to flip the new switches before the storage_backend admin UI lands.
+ */
+
+import { createHash } from 'node:crypto';
+import { Readable } from 'node:stream';
+
+import { Client } from 'minio';
+
+import { env } from '@/lib/env';
+import { NotFoundError } from '@/lib/errors';
+import { logger } from '@/lib/logger';
+import { decrypt } from '@/lib/utils/encryption';
+
+import type { PresignOpts, PutOpts, StorageBackend } from './index';
+
+interface S3BackendConfig {
+  endpoint?: string;
+  region?: string;
+  bucket?: string;
+  accessKey?: string;
+  secretKeyEncrypted?: string;
+  forcePathStyle?: boolean;
+}
+
+interface ResolvedConfig {
+  endpoint: string;
+  port: number;
+  useSSL: boolean;
+  region: string;
+  bucket: string;
+  accessKey: string;
+  secretKey: string;
+}
+
+function decryptIfPresent(stored: string | undefined): string | undefined {
+  if (!stored) return undefined;
+  try {
+    return decrypt(stored);
+  } catch (err) {
+    logger.error({ err }, 'Failed to decrypt S3 secret key');
+    return undefined;
+  }
+}
+
+/**
+ * Convert a possible URL ("https://s3.amazonaws.com:443") to a {host, port,
+ * useSSL} triple suitable for the minio Client.
+ */
+function parseEndpoint(endpoint: string | undefined): {
+  endPoint: string;
+  port: number;
+  useSSL: boolean;
+} {
+  if (!endpoint) {
+    return { endPoint: env.MINIO_ENDPOINT, port: env.MINIO_PORT, useSSL: env.MINIO_USE_SSL };
+  }
+  try {
+    const url = new URL(endpoint);
+    const useSSL = url.protocol === 'https:';
+    const port = url.port ? Number(url.port) : useSSL ? 443 : 80;
+    return { endPoint: url.hostname, port, useSSL };
+  } catch {
+    // Not a URL — treat as bare hostname and use defaults.
+    return { endPoint: endpoint, port: env.MINIO_PORT, useSSL: env.MINIO_USE_SSL };
+  }
+}
+
+function resolveConfig(cfg: S3BackendConfig): ResolvedConfig {
+  const ep = parseEndpoint(cfg.endpoint);
+  return {
+    endpoint: ep.endPoint,
+    port: ep.port,
+    useSSL: ep.useSSL,
+    region: cfg.region ?? 'us-east-1',
+    bucket: cfg.bucket ?? env.MINIO_BUCKET,
+    accessKey: cfg.accessKey ?? env.MINIO_ACCESS_KEY,
+    secretKey: decryptIfPresent(cfg.secretKeyEncrypted) ?? env.MINIO_SECRET_KEY,
+  };
+}
+
+export class S3Backend implements StorageBackend {
+  readonly name = 's3' as const;
+
+  private client: Client;
+  private bucket: string;
+
+  private constructor(client: Client, bucket: string) {
+    this.client = client;
+    this.bucket = bucket;
+  }
+
+  static async create(cfg: S3BackendConfig): Promise<S3Backend> {
+    const resolved = resolveConfig(cfg);
+    const client = new Client({
+      endPoint: resolved.endpoint,
+      port: resolved.port,
+      useSSL: resolved.useSSL,
+      accessKey: resolved.accessKey,
+      secretKey: resolved.secretKey,
+      region: resolved.region,
+    });
+    return new S3Backend(client, resolved.bucket);
+  }
+
+  async put(
+    key: string,
+    body: Buffer | NodeJS.ReadableStream,
+    opts: PutOpts,
+  ): Promise<{ key: string; sizeBytes: number; sha256: string }> {
+    // We need both upload + a sha256 of the bytes. For a Buffer this is trivial;
+    // for a stream we pipe through a hash transform. We buffer streams up to
+    // a reasonable cap (memory pressure is acceptable here — typical files
+    // are under 50MB and the alternative is a temp-file dance).
+    const buffer = Buffer.isBuffer(body) ? body : await streamToBuffer(body);
+    const sha256 = opts.sha256 ?? createHash('sha256').update(buffer).digest('hex');
+
+    await this.client.putObject(this.bucket, key, buffer, buffer.length, {
+      'Content-Type': opts.contentType,
+    });
+
+    return { key, sizeBytes: buffer.length, sha256 };
+  }
+
+  async get(key: string): Promise<NodeJS.ReadableStream> {
+    try {
+      return await this.client.getObject(this.bucket, key);
+    } catch (err) {
+      const code = (err as { code?: string } | null)?.code;
+      if (code === 'NoSuchKey' || code === 'NotFound') {
+        throw new NotFoundError(`Storage object ${key}`);
+      }
+      throw err;
+    }
+  }
+
+  async head(key: string): Promise<{ sizeBytes: number; contentType: string } | null> {
+    try {
+      const stat = await this.client.statObject(this.bucket, key);
+      const meta = (stat.metaData ?? {}) as Record<string, string>;
+      const contentType =
+        meta['content-type'] ?? meta['Content-Type'] ?? 'application/octet-stream';
+      return { sizeBytes: stat.size, contentType };
+    } catch (err) {
+      const code = (err as { code?: string } | null)?.code;
+      if (code === 'NotFound' || code === 'NoSuchKey') return null;
+      throw err;
+    }
+  }
+
+  async delete(key: string): Promise<void> {
+    try {
+      await this.client.removeObject(this.bucket, key);
+    } catch (err) {
+      const code = (err as { code?: string } | null)?.code;
+      if (code === 'NotFound' || code === 'NoSuchKey') return;
+      throw err;
+    }
+  }
+
+  async presignUpload(
+    key: string,
+    opts: PresignOpts,
+  ): Promise<{ url: string; method: 'PUT' | 'POST' }> {
+    const expiry = opts.expirySeconds ?? 900;
+    const url = await this.client.presignedPutObject(this.bucket, key, expiry);
+    return { url, method: 'PUT' };
+  }
+
+  async presignDownload(key: string, opts: PresignOpts): Promise<{ url: string; expiresAt: Date }> {
+    const expiry = opts.expirySeconds ?? 900;
+    const url = await this.client.presignedGetObject(this.bucket, key, expiry);
+    return { url, expiresAt: new Date(Date.now() + expiry * 1000) };
+  }
+
+  /** Used by the admin UI's "Test connection" button. */
+  async healthCheck(): Promise<{ ok: true } | { ok: false; error: string }> {
+    const sentinelKey = `_health/${Date.now()}.txt`;
+    const payload = Buffer.from('ok', 'utf8');
+    try {
+      await this.client.putObject(this.bucket, sentinelKey, payload, payload.length, {
+        'Content-Type': 'text/plain',
+      });
+      const stat = await this.client.statObject(this.bucket, sentinelKey);
+      if (stat.size !== payload.length) {
+        return { ok: false, error: 'sentinel size mismatch' };
+      }
+      await this.client.removeObject(this.bucket, sentinelKey);
+      return { ok: true };
+    } catch (err) {
+      return { ok: false, error: (err as Error).message };
+    }
+  }
+}
+
+async function streamToBuffer(stream: NodeJS.ReadableStream): Promise<Buffer> {
+  const chunks: Buffer[] = [];
+  for await (const chunk of stream as Readable) {
+    chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk as string));
+  }
+  return Buffer.concat(chunks);
+}