- Add DATABENTO_DATASET_MIN_DATES for XNAS.BASIC (2024-07-01) and GLBX.MDP3 (2010-01-01)
- Validate start date against dataset minimum before running backtest
- Parse Databento API errors and show user-friendly messages
- Update date range hint to show dataset-specific availability
- Catch BentoClientError and show appropriate warning tone