Update README with comprehensive Binance exchange support documentation

- Document global --exchange flag (auto/hyperliquid/binance)
- Add exchange routing logic and auto-selection behavior
- Document Binance API integration (spot/futures/options)
- Update config template with binance_api_key and binance_api_secret
- Add real options trading support (Binance only)
- Update cancel order format for both exchanges
- Add exchange support column to command summary table
- Expand data sources table with Binance API endpoints
- Add binance.rs to architecture section
- Include HMAC-SHA256 signing documentation

Author: Michael Yuan