triparnapatra/Secure-User-Authentication ? reverse-engineered prompt

Build me a full stack authentication app with a clean dark theme, where people can sign up, log in, see a protected profile page, and log out.

I want the backend to handle secure registration and login with hashed passwords, JWT based auth, and MongoDB for storing users. Protect the private routes so only signed in users can access them, and make the app show clear success and error messages when something goes wrong.

On the frontend, make a simple responsive React app with pages for login, register, and profile, using API calls to talk to the server. Keep the UI polished but straightforward, and make sure the auth state feels smooth so users stay signed in properly until they log out.

Set it up so I can run the client and server separately, and use environment variables for the database connection, JWT secret, and server port. If you need to check current docs or best practices while building it, go ahead and look them up.