fix(audit-integrations): SMTP/PG/Socket.IO timeouts, prompt injection, secret-at-rest

A focused review of every external integration surfaced six issues the
original audit missed.  Fixed here.

HIGH
* Socket.IO had an unconditional 30-second idle disconnect on every
  socket.  The comment on the line acknowledged it was "for development
  only, would be longer in prod" but no NODE_ENV guard existed, and the
  `socket.onAny` listener only resets on inbound client events — every
  dashboard connection that received only server-push events would have
  been torn down every 30s in production.  Removed the manual idle
  timer entirely; Socket.IO's pingTimeout / pingInterval handles
  dead-transport detection at the protocol level.
* SMTP transporters had no `connectionTimeout` / `greetingTimeout` /
  `socketTimeout`.  Nodemailer's defaults are 2 minutes for connect
  and unlimited for socket — a hung SMTP server would have held a
  BullMQ `email` worker concurrency slot for up to 10 min per job
  (5 retries × 2 min).  Set 10s/10s/30s on both the system transporter
  in `src/lib/email/index.ts` and the user-account transporter in
  `email-compose.service.ts`.

MEDIUM
* PostgreSQL pool had no `statement_timeout` /
  `idle_in_transaction_session_timeout`.  A slow query or transaction
  held by a crashed handler would have eventually exhausted the
  20-connection pool.  30s statement cap, 10s idle-in-tx cap, plus
  `max_lifetime: 30min` to recycle connections.
* `umami_password` and `umami_api_token` were stored as plaintext in
  `system_settings` (the SMTP and S3 secret paths use AES-GCM).  The
  reader now passes them through `readSecret()` which auto-detects
  the encrypted `iv:cipher:tag` shape and decrypts, falling back to
  legacy plaintext so operators can rotate without a flag-day.
* AI email-draft worker interpolated `additionalInstructions` (user-
  controlled) directly into the OpenAI prompt — a hostile rep could
  close the instructions block and inject prompt directives that
  override the system prompt.  Added `sanitizeForPrompt()` that
  strips newlines + quote chars, caps at 500 chars, and the prompt
  now wraps the value in a "treat as data not commands" preamble.

LOW
* Legacy `ensureBucket()` in `src/lib/minio/index.ts` was unguarded —
  if any future code imported it (currently no callers), a misconfigured
  prod deploy could mint a fresh empty bucket.  Now matches the gate
  used by the pluggable S3Backend (`MINIO_AUTO_CREATE_BUCKET=true`
  required) so the legacy export and the new pluggable path agree.

Confirmed not-an-issue: BullMQ Workers create connections via
`{ url }` options object, and BullMQ sets `maxRetriesPerRequest: null`
internally for those — no fix needed.  The shared `redis` singleton
that does keep `maxRetriesPerRequest: 3` is used only for direct
Redis ops (rate-limit sliding window, etc.), never for blocking
BullMQ commands, so the value is correct there.

Test status: 1175/1175 vitest, tsc clean.

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

src/lib/email/index.ts

@@ -12,12 +12,24 @@ import { getPortEmailConfig, type PortEmailConfig } from '@/lib/services/port-co
  * contexts where connection pooling is managed externally (e.g. per-request
  * in serverless, or once at worker startup).
  */
+// Nodemailer's default `connectionTimeout` is 2 minutes and there is no
+// `socketTimeout`, so a hung SMTP server would hold a BullMQ `email`
+// worker concurrency slot for up to 2 min × 5 retry attempts = 10 min
+// per job. With concurrency 5, all slots can be starved by a single
+// flaky upstream. Explicit timeouts cap the worst case under a minute.
+const SMTP_TIMEOUTS = {
+  connectionTimeout: 10_000,
+  greetingTimeout: 10_000,
+  socketTimeout: 30_000,
+} as const;
+
 export function createTransporter(): Transporter {
   return nodemailer.createTransport({
     host: env.SMTP_HOST,
     port: env.SMTP_PORT,
     // Implicitly secure when port is 465; STARTTLS for all other ports.
     secure: env.SMTP_PORT === 465,
+    ...SMTP_TIMEOUTS,
     ...(env.SMTP_USER && env.SMTP_PASS
       ? { auth: { user: env.SMTP_USER, pass: env.SMTP_PASS } }
       : {}),
@@ -29,6 +41,7 @@ function createTransporterFromConfig(cfg: PortEmailConfig): Transporter {
     host: cfg.smtpHost,
     port: cfg.smtpPort,
     secure: cfg.smtpPort === 465,
+    ...SMTP_TIMEOUTS,
     ...(cfg.smtpUser && cfg.smtpPass ? { auth: { user: cfg.smtpUser, pass: cfg.smtpPass } } : {}),
   });
 }