- Add --json CLI flag for structured JSON output across all commands
- Implement JSON formatting functions for different data types:
* Single rate lookups with fallback information
* Unified tax rates (single year and multi-year)
* Last available rates
* Error responses with codes and details
- Add auto-download functionality for missing monthly data in tax calculations
- Modify calculate_tax_yearly_average to automatically fetch missing months
- Add rate limiting (1s delay) between API calls to be respectful
- Update CLI argument parsing and output logic for JSON/text modes
- Maintain full backward compatibility - existing commands work unchanged
- Enhance documentation with JSON usage examples and schema
- Update help text to include new --json option
Features:
- JSON output for programmatic consumption
- Automatic data fetching for incomplete years
- Structured error handling
- Comprehensive documentation updates
Breaking changes: None (fully backward compatible)
