proggettopiano/boh-emerg — reverse-engineered prompt

Build me a simple full stack web app from this repo and make sure it runs cleanly locally and can be deployed with the frontend and backend separated.

The frontend should talk to the backend through an environment variable called REACT_APP_API_URL, not a hardcoded URL. The backend should read MONGO_URL and DB_NAME from its environment, and it should allow the frontend through BACKEND_CORS_ORIGINS so it works both locally and on a hosted site.

Please inspect the existing frontend and backend folders, keep the current project style, and wire up whatever is missing so the app actually loads, connects to the API, and stores data in MongoDB if the backend already expects that. Add clear setup steps in the README for local development and deployment. If anything is broken, fix it rather than rewriting everything from scratch.

Run the tests or basic smoke checks before finishing, and look up current docs online if you need to.