fix(audit-wave-11): dossier sweep — error-ux + webhook + storage + search + maintainability

Final pass over the unaddressed AUDIT-2026-05-12 dossiers, taking the
tractable Critical/High items from each:

error-ux-auditor (5 items)
- C2: 17 toast.error(err.message) sites swept to toastError(err, …) so
  every user-visible failure carries a copy-paste Reference ID
- C3: apiFetch synthesizes a client-side correlation id when a 5xx
  comes back with a non-JSON body (reverse-proxy HTML pages); message
  becomes "The server is unreachable. Please try again." with code
  UPSTREAM_UNREACHABLE
- C4: checkRateLimit fails OPEN when Redis is unavailable so an outage
  no longer 500s login + portal sign-in; logged at warn so monitoring
  catches it
- H2: StorageTimeoutError (name='TimeoutError') replaces the plain
  Error throw in s3.ts withTimeout — error-classifier hints fire now
- H5: errorResponse() adopted across /api/storage/[token],
  /api/public/website-inquiries, and the Documenso webhook body (drops
  the "Invalid secret" reconnaissance string)

outbound-webhook-auditor (5 items)
- C1: signature is now HMAC(secret, `${ts}.${body}`) with the
  timestamp surfaced as X-Webhook-Timestamp so receivers can reject
  replays outside a freshness window
- C3: dead-letter with reason missing_signing_secret when secret is
  null (defence-in-depth against DB tampering / future migration
  mistakes)
- H2: webhooks queue bumped to maxAttempts=8 with 30 s base
  exponential backoff so a 30 s receiver blip during a deploy no
  longer dead-letters every in-flight event; per-queue
  backoffDelayMs added to QUEUE_CONFIGS
- M1: SSRF denylist gains Oracle Cloud metadata 192.0.0.192
- M2: dispatch-time https:// assertion before fetch, so a bad DB edit
  can't slip plaintext through

storage-pathing-auditor (2 items)
- H1: berth-PDF presigned-upload keys now `${portSlug}/berths/…/…`
  with portSlug threaded into backend.presignUpload — engages the
  filesystem-proxy port-binding `p` token verifier
- H2: presignDownloadUrl auto-derives portSlug from the key's first
  segment when callers don't pass it, so all 8 download sites engage
  the `p`-token guard without per-site plumbing

search-auditor (1 item)
- H3: removed dead void wantEmail; void wantPhone; pair plus the
  unused looksLikeEmail helper — the bucket-reorder it was scaffolded
  for was never wired

maintainability-auditor (1 item)
- M2: swept seven abandoned `void <symbol>` markers and their dead
  imports across clients/bulk, interests/bulk, admin/email-templates,
  admin/website-submissions, alert-rules, and notes.service

Deferred to future work (substantial refactors, schema migrations, or
multi-file UI work):
- error-ux M3-M8 (global-error.tsx, per-route loading.tsx coverage,
  ErrorBanner component, /api/ready route, worker DLQ admin surface)
- maintainability C1-C4 (documents/search/notes service splits,
  interest-tabs split — multi-hour refactors)
- currency C1-H5 (mixed-currency dashboard aggregation, FX history
  table, rounding policy) — wait for second non-USD port
- outbound-webhook C2 (deliveries reaper job), H1 (DNS-rebind TOCTOU
  with undici Agent), H3 (circuit-breaker), H5 (presigned-post-policy)
- storage-pathing C2 (orphan reaper), H3-H5 (streaming + content-type
  binding)

Tests: 1315/1315 vitest ✅ ; tsc clean.

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

src/lib/api/client.ts

@@ -85,18 +85,41 @@ export async function apiFetch<T = unknown>(url: string, opts: ApiFetchOptions =
   });
 
   if (!res.ok) {
-    const error = (await res.json().catch(() => ({ error: res.statusText }))) as {
+    // error-ux-auditor C3: reverse-proxy 502/504 pages deliver HTML, not
+    // JSON. The previous code silently degraded to
+    // `{error: res.statusText}` which surfaced "Bad Gateway" with no
+    // requestId and no copy-pasteable correlation handle. Detect the
+    // proxy-error shape (5xx + JSON parse fail) and synthesize a
+    // client-side correlation id so the toast still has *something* the
+    // user can quote to support.
+    const error = (await res.json().catch(() => null)) as {
       error?: string;
       message?: string;
       code?: string;
       details?: unknown;
       requestId?: string;
       retryAfter?: number;
-    };
-    // Surface the request id so toasts can display "Error ID: …" and
-    // the user can copy it to a support ticket. Server-side wrappers
-    // always set X-Request-Id, even on early-return 401/403 paths.
-    const requestId = error.requestId ?? res.headers.get('x-request-id') ?? null;
+    } | null;
+    const upstreamRequestId = res.headers.get('x-request-id');
+    if (error === null) {
+      const isProxyFailure = res.status >= 500;
+      // Short, copy-pasteable client-side handle so support can grep
+      // the front-end logs even when the proxy never reached our app.
+      const synthId =
+        upstreamRequestId ??
+        `client-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 8)}`;
+      throw new ApiError({
+        message: isProxyFailure
+          ? 'The server is unreachable. Please try again.'
+          : res.statusText || 'Request failed',
+        status: res.status,
+        code: isProxyFailure ? 'UPSTREAM_UNREACHABLE' : null,
+        details: null,
+        requestId: synthId,
+        retryAfter: null,
+      });
+    }
+    const requestId = error.requestId ?? upstreamRequestId ?? null;
     throw new ApiError({
       message: error.error ?? error.message ?? 'Request failed',
       status: res.status,