vinikuttyraja5345-design/MERN-STACK-CRM-Backend ? reverse-engineered prompt

Build me the backend for a simple CRM app.

I want a Node and Express API that connects to MongoDB, handles user login and signup, and lets me create, view, update, and delete CRM records like customers, leads, or contacts. Please organize it cleanly with models, routes, controllers, middleware, and config so it is easy to extend later.

Make sure the API has basic validation, error handling, and protected routes for signed in users. If it makes sense, add JWT based authentication and role checks for things like admin versus normal user. I also want the server to be easy to run locally, with environment variable support and a clear startup file.

Please keep the code simple and production friendly, and use current best practices for a MERN backend. If you need to check the latest docs for anything, go ahead and look them up online first.