Add sites/coingecko package with GetPrice() method that extracts
structured crypto price data (name, symbol, price, 24h/7d change,
market cap, volume, 24h high/low) from CoinGecko coin pages.
Includes mock-based tests and parseLargeNumber helper for T/B/M suffixes.
Closes#27
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
