🎨 Add API Settings GUI with test buttons

NEW GUI:
- API key configuration panel
- Test buttons for all networks
- Live balance checking
- Price API testing
- Seed derivation testing
- Dark theme interface
- Results display

FEATURES:
- Configure API keys (optional - free APIs work without keys)
- Test ETH, BTC, BSC, POLYGON, etc.
- Test price API (CoinGecko)
- Test seed phrase derivation
- View examples and documentation
- Save settings to api_config.json

ALL TESTS PASSED:
✅ Balance checker works with free APIs
✅ Seed derivation works correctly
✅ Performance optimizer prevents overload
✅ Auto balance integration functional
✅ Multiple networks supported

Ready to build!

Author: LulzSec1337