feat(gateway): tier-detector with fail-fast PG/Valkey/pgvector probes (FED-M1-04)

Implements `apps/gateway/src/bootstrap/tier-detector.ts` invoked from
`main.ts` before NestJS bootstraps. For each tier:

- `local`: no-op (PGlite is in-process)
- `standalone`: probe Postgres + Valkey
- `federated`: probe Postgres + Valkey + pgvector extension; reject
  config upfront if `queue.type !== 'bullmq'`

Each probe has a 5-second hard cap and emits a structured
`TierDetectionError` with service / host / port / remediation. The
remediation field discriminates pgvector failure modes ("library not
available" vs "permission denied") so operators get actionable hints
without leaking credentials.

Adds `postgres` and `ioredis` as direct gateway deps; previously only
transitive. 12 unit tests cover happy paths and each fail-fast branch.

Refs #460

apps/gateway/package.json

@@ -63,8 +63,10 @@
     "class-validator": "^0.15.1",
     "dotenv": "^17.3.1",
     "fastify": "^5.0.0",
+    "ioredis": "^5.10.0",
     "node-cron": "^4.2.1",
     "openai": "^6.32.0",
+    "postgres": "^3.4.8",
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",
     "socket.io": "^4.8.0",