[umeraamir09]

Summary

• Add a multi-stage production Docker image and a central Compose stack for UmrFlix, Postgres, schema migration, and media services.
• Replace the self-hosted Convex backend with Postgres-backed document stores for sessions, user data, discovery, and watch-party snapshots; add schema, migrations, maintenance, and database tests.
• Call TMDB directly with server-side credentials, update health checks and deployment/environment documentation, and remove obsolete Convex, proxy, and deployment files.

Tests

• Adds npm run test:db and TMDB API tests; tests were not run as part of opening this PR.