feat: add PostgreSQL persistence for permanent shareable links

- Add PostgreSQL service to docker-compose with health checks
- Add migrate service that runs prisma migrate deploy on startup
- Integrate Prisma client in worker: checks for existing generations
  (same repo+commit) before regenerating, writes to Postgres on completion
- Update /api/docs/[id] with Redis → PostgreSQL fallback + cache repopulation
- Update Dockerfile: prisma generate in build, copy Prisma engine to worker/web
- Add @codeboard/database dependency to web and worker packages
- Add initial SQL migration for Generation and User tables
- Change removeOnComplete to { age: 3600 } for job retention

packages/database/prisma/migrations/migration_lock.toml

@@ -0,0 +1,3 @@
+# Please do not edit this file manually
+# It should be added in your version-control system (i.e. Git)
+provider = "postgresql"