shivani-1508444/real-time-notification-dashboard ? reverse-engineered prompt

Build me a real time notification dashboard where an admin can type a short announcement and send it out to everyone watching the app. I want the message to pop up instantly as a toast on every open user tab, and I want those notifications to also be saved so users can refresh later and still see the full history.

Please make it feel clean and simple, with separate admin and user screens, a basic navbar, loading and error states, and some input validation so empty messages can’t be sent. I also want the history view to show past notifications from the backend, and it should work across multiple browser tabs at the same time.

Use a normal full stack setup with a React frontend, a Node and Express backend, MongoDB for storage, and Socket.io for the live updates. If you need current setup details, look up the latest docs online and wire it up in a way that runs locally with a clear dev setup.