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/lib/db/migrations/0041_role_permissions_edit_keys.sql

@@ -13,6 +13,13 @@
 -- jsonb_set with create_missing=true (the default) inserts the key only
 -- when it's absent, so re-runs are idempotent and the migration is safe
 -- against a partial run.
+--
+-- Note: per-port overrides live in `port_role_overrides.permission_overrides`
+-- and are PARTIAL — they only contain the keys a port flipped from the
+-- base role. The deepMerge resolver fills in `documents.edit` from the
+-- base role for any port that didn't override it, so we deliberately do
+-- NOT touch `port_role_overrides` here. Backfilling there would synthesize
+-- override entries that the operator never intended.
 
 UPDATE roles
 SET permissions = jsonb_set(
@@ -33,26 +40,3 @@ SET permissions = jsonb_set(
 )
 WHERE permissions->'files' IS NOT NULL
   AND NOT (permissions->'files' ? 'edit');
-
--- Same backfill on per-port overrides (`port_role_overrides.permissions`)
--- so an override that flipped a sibling permission stays consistent.
-
-UPDATE port_role_overrides
-SET permissions = jsonb_set(
-  permissions,
-  '{documents,edit}',
-  COALESCE(permissions->'documents'->'create', 'false'::jsonb),
-  true
-)
-WHERE permissions->'documents' IS NOT NULL
-  AND NOT (permissions->'documents' ? 'edit');
-
-UPDATE port_role_overrides
-SET permissions = jsonb_set(
-  permissions,
-  '{files,edit}',
-  COALESCE(permissions->'files'->'upload', 'false'::jsonb),
-  true
-)
-WHERE permissions->'files' IS NOT NULL
-  AND NOT (permissions->'files' ? 'edit');