newsdatahub/newsdatahub-news-aggregator — reverse-engineered prompt

Build me a polished news reader web app that uses the NewsDataHub API, with a backend in front of it so the API key stays hidden and requests can be cached. I want it to work in two modes, a demo mode that works without any key using sample or cached data, and a live mode that pulls real news when a key is added.

The app should feel modern and easy to use on phone and desktop, with dark mode, responsive layout, and both grid and list views. Let people search news with simple boolean queries using AND, OR, and NOT, then filter by country, language, political leaning, date range, topic, and source type. Show clean loading states, handle errors nicely, and keep the interface fast with debounced search and sensible caching so repeat searches do not hammer the API.

Please make it easy to run locally with Docker, and include enough test coverage that it feels production ready. If you need details, look up the current NewsDataHub docs online.