Er-AjayQA/EcommerceApplicationAdvanceBackendLearning ? reverse-engineered prompt

Build me the backend for a simple ecommerce app in this repo.

I want a clean TypeScript server that can handle basic shopping flows like user signup and login, browsing products, adding items to a cart, placing an order, and checking order history. It should feel like a real starter backend for learning, with sensible structure, validation, error handling, and a few example routes and controllers so I can expand it later.

Please set it up inside the backend folder, include a clear way to run it locally, and make sure the code is easy to understand. If you need to check current docs for any libraries or setup details, go ahead and look them up online. Also add a simple README or setup notes so I know how to start the server and test the main endpoints.