feat(cron): Enhance scheduled tasks with create/edit dialog and presets
- Add TaskDialog component for creating/editing cron jobs
- Implement schedule presets (every minute, hourly, daily, weekly, monthly)
- Add human-readable cron schedule parsing
- Enhance CronJobCard with run now, edit, delete actions
- Add failed tasks counter to statistics
- Show last run success/failure with timestamps
- Integrate channel selection for task targets
- Add gateway connection status awareness
- Update process.md to reflect project completion
