fix(audit-verification): regressions found in post-Tier-6 review

Two parallel reviews of the Tier 0–6 work surfaced one CRITICAL
regression and a handful of remaining cross-tenant gaps that the
original audit didn't enumerate. All fixed here:

CRITICAL
* document-reminders.processReminderQueue — the new bulk-fetch
  leftJoin to documentTemplates was scoped on `templateType` alone.
  Templates of the same type exist in every port; the cartesian
  explosion would have fired one Documenso reminder PER matching
  template-row per cron tick (a 5-port deploy = 5 reminders to the
  same signer per cycle). Added eq(documentTemplates.portId, portId)
  to the join.
* All five remaining Documenso webhook handlers (RecipientSigned /
  Completed / Opened / Rejected / Cancelled) accept and require an
  optional portId now, with a shared resolveWebhookDocument() helper
  that refuses to mutate when the lookup is ambiguous across tenants
  without a resolved port. Tier 5's port-scoping was applied only to
  Expired; the route now forwards the matched portId to every
  handler. Tightens the WHERE clauses on subsequent UPDATEs to (id,
  portId) for defense-in-depth.

HIGH
* verifyDocumensoSecret rejects when `expected` is empty —
  timingSafeEqual(0-bytes, 0-bytes) was returning true, so a dev env
  with a blank DOCUMENSO_WEBHOOK_SECRET would accept a request whose
  X-Documenso-Secret header was also missing/empty.
  listDocumensoWebhookSecrets skips the env entry when blank.
* /api/public/health — the website-intake-secret comparison was a
  string `===` (not constant-time). Switched to timingSafeEqual via
  Buffer.from().

MEDIUM
* server.ts SIGTERM ordering — Socket.io closes BEFORE the HTTP
  drain so long-poll websockets stop holding the server open past
  the compose stop_grace_period.
* /api/v1/me PATCH preferences merge — allow-list filter on the
  merged JSONB so legacy rows from the old .passthrough() era stop
  silently re-shipping their bloat to disk.

Migration fixes (deploy-blocking)
* 0041 referenced `port_role_overrides.permissions` (column is
  `permission_overrides`) — overrides are partial JSONB and don't
  need backfilling at all (deepMerge resolves edit from the base
  role). Removed the override UPDATEs entirely.
* 0042 switched all FK + CHECK adds to NOT VALID + VALIDATE so the
  brief table-lock phase is decoupled from the row-scan validation,
  giving a cleaner abort-and-restart story if a constraint catches
  dirty production data. Added a pre-cleanup UPDATE for
  invoices.billing_entity_id = '' rows (backfills from clientName,
  falls back to the row id) so the new non-empty CHECK passes on a
  dirty table.

Test status: 1175/1175 vitest, tsc clean.

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

src/app/api/v1/me/route.ts

@@ -62,13 +62,20 @@ export const PATCH = withAuth(async (req, ctx: AuthContext) => {
     if (body.phone !== undefined) updates.phone = body.phone;
     if (body.avatarUrl !== undefined) updates.avatarUrl = body.avatarUrl;
     if (body.preferences !== undefined) {
-      const merged = {
-        ...((profile.preferences as Record<string, unknown>) ?? {}),
-        ...body.preferences,
-      };
-      // Hard cap on the merged JSONB to defend against historical rows
-      // bloated by the previous .passthrough() schema. 8 KB is generous
-      // — current legitimate keys are 3 booleans/strings.
+      // Allow-list — only retain keys defined in the strict schema. Pre-
+      // strict rows may carry extra keys from when the schema was
+      // .passthrough(); the merge prunes them so legacy bloat doesn't
+      // accumulate forever, and a future schema regression that tries
+      // to ship arbitrary keys still gets dropped here at write time.
+      const ALLOWED_PREF_KEYS = new Set(['dark_mode', 'locale', 'timezone']);
+      const existing = (profile.preferences as Record<string, unknown>) ?? {};
+      const merged = Object.fromEntries(
+        Object.entries({ ...existing, ...body.preferences }).filter(([k]) =>
+          ALLOWED_PREF_KEYS.has(k),
+        ),
+      );
+      // Hard cap on the merged JSONB — defense in depth against any
+      // future schema growth that might re-introduce free-form keys.
       const serialized = JSON.stringify(merged);
       if (Buffer.byteLength(serialized, 'utf8') > 8 * 1024) {
         throw new ValidationError('preferences exceeds 8KB');