fix(audit-tier-1): timeouts, lifecycle, per-port Documenso, FK constraints

Closes the second wave of HIGH-priority audit findings:

* fetchWithTimeout helper (new src/lib/fetch-with-timeout.ts) wraps
  Documenso, OCR, currency, Umami, IMAP, etc. — a hung upstream can
  no longer pin a worker concurrency slot indefinitely.  OpenAI client
  passes timeout: 30_000.  ImapFlow gets socket / greeting / connection
  timeouts.
* SIGTERM / SIGINT handler in src/server.ts drains in-flight HTTP,
  closes Socket.io, and disconnects Redis before exit; compose
  stop_grace_period bumped to 30s.  Adds closeSocketServer() helper.
* env.ts gains zod-validated PORT and MULTI_NODE_DEPLOYMENT, and
  filesystem.ts now reads from env (a typo can no longer silently
  disable the multi-node guard).
* Per-port Documenso template + recipient IDs land in system_settings
  with env fallback (PortDocumensoConfig now exposes eoiTemplateId,
  clientRecipientId, developerRecipientId, approvalRecipientId).
  document-templates.ts uses the per-port config and threads portId
  into documensoGenerateFromTemplate().
* Migration 0042 wires the eleven HIGH-tier missing FK constraints
  (documents/files/interests/reminders/berth_waiting_list/
  form_submissions) plus polymorphic CHECK round 2
  (yacht_ownership_history.owner_type, document_sends.document_kind),
  invoices.billing_entity_id NOT EMPTY, and clients.merged_into self-FK.
  Drizzle schema columns updated to .references(...) where possible
  so the misleading "FK wired in relations.ts" comments are gone.

Test status: 1168/1168 vitest, tsc clean.

Refs: docs/audit-comprehensive-2026-05-05.md HIGH §§5,6,7,8,9,10 +
MED §§14,15,16,18.

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

src/lib/storage/filesystem.ts

@@ -189,7 +189,12 @@ export class FilesystemBackend implements StorageBackend {
 
   /** 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') {
+    // Read from the zod-validated env, not raw process.env — a typo
+    // (MULTI_NODE_DEPLOY=true, MULTINODE_DEPLOYMENT=true) used to silently
+    // pass the string-equality check, leaving the multi-node guard
+    // disabled. The schema in src/lib/env.ts now coerces the value and
+    // rejects unknown shapes at boot.
+    if (env.MULTI_NODE_DEPLOYMENT) {
       throw new Error(
         'FilesystemBackend cannot start when MULTI_NODE_DEPLOYMENT=true. ' +
           'Use an S3-compatible backend for multi-node deployments.',