Implement complete event series endpoints with full CRUD support
## Backend Implementation
- Add dedicated series endpoints: create, update, delete
- Implement RFC 5545 compliant RRULE generation and modification
- Support all scope operations: this_only, this_and_future, all_in_series
- Add comprehensive series-specific request/response models
- Implement EXDATE and RRULE modification for precise occurrence control
## Frontend Integration
- Add automatic series detection and smart endpoint routing
- Implement scope-aware event operations with backward compatibility
- Enhance API payloads with series-specific fields
- Integrate existing RecurringEditModal for scope selection UI
## Testing
- Add comprehensive integration tests for all series endpoints
- Validate scope handling, RRULE generation, and error scenarios
- All 14 integration tests passing
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
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