- Add GET /auth/status endpoint (returns needsSetup when no admin exists)
- Add POST /auth/setup endpoint (public first-admin registration)
- Add IsAdminExists + SetupInitialAdmin methods to AuthService
- Frontend: detect needsSetup on load, show setup page with admin registration
- Frontend: fall back to login page when setup is already complete
- Docker compose: env_file already optional (required: false), no changes needed
- Bootstrap: auto-detect BOOTSTRAP_CLUSTERS without separate enable flag