sunnypra09-ux/advance-mern-auth ? reverse-engineered prompt

Build me a full login and registration app with a separate backend and frontend, using a modern MERN setup.

I want users to be able to sign up, log in, stay signed in, and log out cleanly. Please add the usual auth flow, basic protected pages, and a simple, polished UI for the frontend. On the backend, set up the authentication logic, validation, password handling, and whatever is needed to keep sessions or tokens secure. Make the app feel complete enough to run locally right away, with clear env setup and sensible defaults.

If you need to, look up current best practices for auth in the MERN stack so the setup is solid and up to date. Keep it simple, clean, and ready to extend later.