varunnandanthota-08/MERN-Authentication ? reverse-engineered prompt

Build me a simple full stack login and signup app with a clean frontend and a small backend.

I want users to be able to create an account, log in, stay signed in, and log out. Show a basic protected page after login, and make sure someone who is not signed in gets sent back to the login screen. Add friendly error messages for things like wrong password, missing fields, or duplicate email. Keep the UI simple and modern, with forms that are easy to use on desktop and mobile.

Use a separate client and server setup, and wire them together so the auth flow actually works end to end. If you need to check current best practices or docs while building it, go ahead and look them up online. Make it feel like a real app someone could start from and extend later.