feat: Complete import functionality with RRULE fixes and comprehensive testing

- Fix RRULE BYDAY filtering for daily frequency events (Tether sync weekdays only)
- Fix timezone transfer in recurring event expansion
- Add comprehensive timezone-aware iCal generation
- Add extensive test suite for recurrence and timezone functionality
- Update dependencies and configuration examples
- Implement cleanup logic for orphaned events
- Add detailed import plan documentation

This completes the core import functionality with proper timezone handling,
RRULE parsing, and duplicate prevention mechanisms.

config/example.toml

@@ -91,6 +91,6 @@ enabled = true
 # Import behavior settings
 overwrite_existing = true    # Source always wins - overwrite target events
 delete_missing = false       # Don't delete events missing from source
-dry_run = false              # Set to true for preview mode
+
 batch_size = 50              # Number of events to process in each batch
 create_target_calendar = true # Create target calendar if it doesn't exist