Prepare this app for deployment to [platform]. Do not change features.

  1. List every environment variable the app reads. Create .env.example with placeholder values, confirm .env is in .gitignore.
  2. Make the server listen on process.env.PORT and bind to 0.0.0.0, not localhost.
  3. Confirm build/start commands are correct and the start command doesn't run a dev server.
  4. Add a GET /health endpoint that returns 200 without touching external services.
  5. Make migrations a separate step, not something that runs on every boot.
  6. Pin the runtime version (engines field, .nvmrc, or .python-version). Show me the diff before applying.