Backend changes:
- Add "Custom" frequency option to database seeds
- Add custom_interval_days field to Task model
- Update task DTOs to accept custom_interval_days
- Update task service to use custom_interval_days for next due date calculation
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>