1. Create secret env-files (never commit):
   backend/.env   # OPENAI_API_KEY, …
   frontend/.env  # NEXT_PUBLIC_API_URL=http://backend:2024
2. Build & start:
   docker compose up --build
   OR
   docker compose up --build --no-deps --force-recreate
3. Access:
   • http://localhost:3000 – UI
   • http://localhost:2024 – backend API (health-check at /healthz)