Removes all mock price simulation features:
- Delete MockPriceManager from backend/data/
- Remove mock_mode, enable_mock, is_mock_mode flags from services
- Remove mock CLI options and config
- Remove mock mode UI components and state from frontend
- Update tests to remove mock references
Now system supports only live and backtest modes.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>