rollendxavier/crypto-portfolio-tracker-react — reverse-engineered prompt

Build me a simple crypto portfolio tracker dashboard that runs in the browser. I want to be able to add or follow my favorite coins, see their current prices update from CoinGecko, and click into a coin to view historical price data in a clean chart. Keep the design modern and easy to read, like a personal crypto watchlist I can check quickly.

Please make it easy to set my CoinGecko API key in one obvious place, and have the app load nicely with sensible defaults so I can try it right away. Show useful details like coin name, symbol, price, and basic change info, and make sure the app handles loading states and API errors without feeling broken. If the repo already has starter code or images, use them and finish it into a polished working app. Also include short setup steps so I can run it locally with npm. If anything about the API changed, look up the current CoinGecko docs online and wire it up correctly.