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/env.ts

@@ -65,6 +65,22 @@ const envSchema = z.object({
   PUBLIC_SITE_URL: z.string().url(),
   NODE_ENV: z.enum(['development', 'production', 'test']).default('development'),
   LOG_LEVEL: z.enum(['fatal', 'error', 'warn', 'info', 'debug', 'trace']).default('info'),
+  /**
+   * HTTP listener port. zod-coerced from PORT so a typo (`PORT=foo`) hard-
+   * fails at boot rather than silently listening on an ephemeral port.
+   */
+  PORT: z.coerce.number().int().positive().default(3000),
+  /**
+   * When true, the filesystem storage backend refuses to start (per
+   * src/lib/storage/filesystem.ts:192). Reading via the zod schema means
+   * a typo on the env var hard-fails at boot rather than silently
+   * disabling the multi-node guard. Per CLAUDE.md, multi-node deploys
+   * MUST use the s3-compatible backend.
+   */
+  MULTI_NODE_DEPLOYMENT: z
+    .enum(['true', 'false'])
+    .default('false')
+    .transform((v) => v === 'true'),
 });
 
 export type Env = z.infer<typeof envSchema>;