fix(audit-v3): platform-wide deferred-list cleanup (rounds 1-4)

Working through the audit-v2 deferred backlog. Each round was tested
(typecheck + 1168/1168 vitest) before moving on.

Round 1 — DB performance + AI cost visibility:
- Add missing FK indexes Postgres doesn't auto-create on
  berth_reservations.{interest_id, contract_file_id},
  documents.{file_id, signed_file_id}, document_events.signer_id,
  document_templates.source_file_id, form_submissions.{form_template_id,
  client_id}, document_sends.{brochure_id, brochure_version_id,
  sent_by_user_id}. Without these, RESTRICT-checks on parent delete +
  reverse-lookups walk the child tables fully. Migration 0037.
- AI worker now writes one ai_usage_ledger row per OpenAI call so admins
  can audit spend per port/user/feature and future per-port budgets have
  history to read from. Failure to write is logged-not-thrown so the
  user-facing email draft is unaffected.

Round 2 — Boot-time + transport hardening:
- S3 backend verifies the bucket exists at startup (or auto-creates
  when MINIO_AUTO_CREATE_BUCKET=true). A typo'd bucket name now
  surfaces with a clear boot error instead of a vague Minio error
  inside the first user-facing request.
- Documenso v1 placeFields: 3-attempt exponential-backoff retry on 5xx
  + network errors, fail-fast on 4xx. Stops one transient flake from
  leaving a document with a partial field set.
- FilesystemBackend logs a structured warn-once at boot when the dev
  HMAC fallback is in effect, so two processes started with different
  BETTER_AUTH_SECRET values are observable (random 401s on file
  downloads otherwise).
- Logger redact paths extended to cover *.headers.{authorization,
  cookie}, *.config.headers.authorization, encrypted-credential blobs
  (secretKeyEncrypted, smtpPassEncrypted, etc.), the Documenso
  X-Documenso-Secret header, and 2-level nested forms.

Round 3 — UI feedback + permission gates:
- Storage admin migrate dialog: success toast with row count + error
  toast on both dryRun and migrate mutations.
- Invoice detail Send + Record-payment buttons wrapped in
  PermissionGate (invoices.send / invoices.record_payment); both
  mutations now toast on success/error.
- Admin user list Edit button wrapped in PermissionGate(admin.manage_users).
- Scan-receipt page surfaces an amber warning when OCR fails so reps
  know they can fill the form manually instead of staring at a stalled
  spinner; the editable form now also opens on scanMutation.isError
  / uploadedFile, not only on success.
- Email threads list now renders skeleton rows during load + shared
  EmptyState for the empty case (was a single "Loading…" line).

Round 4 — Service / route correctness:
- documentSends.sent_by_user_id was a free-text NOT NULL column with no
  FK. Now nullable + FK to user(id) ON DELETE SET NULL so the audit row
  survives a user being hard-deleted. Migration 0038 with a defensive
  null-out for any orphan ids before attaching the constraint.
- Saved-views route: documented why withAuth alone is correct (the
  service strictly filters by (portId, userId) — owner-only by design).
- Public-interests audit log: replaced "userId: null as unknown as
  string" cast with userId: null; AuditLogParams already accepts null
  for system-generated events.
- EOI in-app PDF fill: extracted setBerthRange() that, when the
  AcroForm field is missing AND the context has a non-empty range
  string, logs a structured warn so the deployment gap (live Documenso
  template needs the field) is observable instead of silently dropping
  the multi-berth range.

Test status: 1168/1168 vitest. tsc clean. Two new migrations
(0037/0038) need pnpm db:push (or migration apply) on the dev DB.
Deferred-doc updated with the remaining open items (bigger refactors).

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

src/components/email/email-threads-list.tsx

@@ -5,6 +5,8 @@ import { formatDistanceToNow } from 'date-fns';
 import { Mail } from 'lucide-react';
 
 import { apiFetch } from '@/lib/api/client';
+import { EmptyState } from '@/components/shared/empty-state';
+import { Skeleton } from '@/components/ui/skeleton';
 
 interface Thread {
   id: string;
@@ -27,20 +29,32 @@ export function EmailThreadsList() {
   });
 
   if (isLoading) {
-    return <p className="text-sm text-muted-foreground">Loading threads…</p>;
+    // Skeleton rows shaped like the real list so the layout doesn't pop.
+    return (
+      <div className="rounded-lg border divide-y">
+        {Array.from({ length: 4 }).map((_, i) => (
+          <div key={i} className="p-3 space-y-2">
+            <div className="flex items-center justify-between gap-2">
+              <Skeleton className="h-4 w-1/3" />
+              <Skeleton className="h-3 w-16" />
+            </div>
+            <Skeleton className="h-3 w-1/2" />
+            <Skeleton className="h-3 w-2/3" />
+          </div>
+        ))}
+      </div>
+    );
   }
 
   const threads = data?.data ?? [];
 
   if (threads.length === 0) {
     return (
-      <div className="rounded-lg border border-dashed p-8 text-center text-muted-foreground">
-        <Mail className="mx-auto h-6 w-6 mb-2" />
-        <p className="text-sm">No email threads yet.</p>
-        <p className="text-xs">
-          Connect an account and trigger a sync to see incoming threads here.
-        </p>
-      </div>
+      <EmptyState
+        icon={Mail}
+        title="No email threads yet"
+        description="Connect an account and trigger a sync to see incoming threads here."
+      />
     );
   }