phase 5 prep: backfill-users.ts + deployment runbook in .memory

- scripts/backfill-users.ts: 扫 PG users 表,对每人幂等调 orchestrator POST /users
- orchestrator/package.json: 加 postgres 依赖
- .memory/project.md: Phase 3/4 完成状态,Phase 5 上线 checklist

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

orchestrator/package.json

@@ -12,6 +12,7 @@
     "@aws-sdk/client-s3": "^3.670.0",
     "@aws-sdk/s3-request-presigner": "^3.670.0",
     "hono": "^4.6.0",
+    "postgres": "^3.4.5",
     "zod": "^3.23.0"
   },
   "devDependencies": {