sanjayyy04/ChatApp-MERN-complate ? reverse-engineered prompt

Build me a full stack chat app where people can sign up, log in, and message each other in a clean, simple interface.

I want the app to feel like a modern messaging product, with a list of conversations on one side, the active chat on the other, and messages updating smoothly in real time. Make it responsive so it still works well on smaller screens. Add the basic things a normal chat app needs, like user authentication, sending and receiving messages, and a clear way to see who you are chatting with.

Please set it up as a complete working project with a frontend and backend, and make sure it can be run locally without too much fuss. If you need current docs or setup details, look them up online. Also include whatever environment setup is needed so I can start it easily, and make it easy to run with Docker too if that fits the project.