skillmantracode/mern-trainining ? reverse-engineered prompt

Build me a simple MERN stack training app that shows a full working example of how the pieces fit together.

I want a React frontend and a Node and Express backend with MongoDB for data storage. The app should let me view a list of items, add new ones, edit them, and delete them, so it feels like a realistic hands on practice project. Make the UI clean and easy to use, and keep the code organized in a way that would be good for learning and extending later.

Please set it up so the frontend talks to the backend with API calls, and the backend handles the database work properly. If you need to check the latest docs for anything, go ahead and look them up online. Include enough sample data and basic validation so I can run it and learn from it right away.