Fix PostgreSQL port exposure in docker-compose - #2530

• Fix PostgreSQL port exposure in docker-compose
• fix defaults

Summary by cubic

Stop exposing PostgreSQL in docker-compose and align DB defaults. This reduces the attack surface and clarifies the self-hosting setup.

• Migration
  • If you were connecting via localhost:5432, use docker compose exec nuq-postgres psql instead (or add a temporary, firewalled port mapping).
  • Ensure POSTGRES_USER, POSTGRES_PASSWORD, and POSTGRES_DB match between your .env and docker-compose; defaults are now firecrawl/firecrawl_password/firecrawl, and USE_DB_AUTHENTICATION defaults to false.

^{Written for commit e87a7a7. Summary will update automatically on new commits.}