feat(#115,#116): implement cron scheduler worker and WebSocket notifications
## Issues Addressed
- #115: Cron scheduler worker
- #116: Cron WebSocket notifications
## Changes
### CronSchedulerService (cron.scheduler.ts)
- Polls CronSchedule table every minute for due schedules
- Executes commands when schedules fire (placeholder for MoltBot integration)
- Updates lastRun/nextRun fields after execution
- Handles errors gracefully with logging
- Supports manual trigger for testing
- Start/stop lifecycle management
### WebSocket Integration
- Added emitCronExecuted() method to WebSocketGateway
- Emits workspace-scoped cron:executed events
- Payload includes: scheduleId, command, executedAt
### Tests
- cron.scheduler.spec.ts: 9 passing tests
- Tests cover: status, due schedule processing, manual trigger, scheduler lifecycle
## Technical Notes
- Placeholder triggerMoltBotCommand() needs actual implementation
- Uses setInterval for polling (could upgrade to cron-parser library)
- WebSocket rooms use workspace:{id} format (existing pattern)
## Files Changed
- apps/api/src/cron/cron.scheduler.ts (new)
- apps/api/src/cron/cron.scheduler.spec.ts (new)
- apps/api/src/cron/cron.module.ts (updated)
- apps/api/src/websocket/websocket.gateway.ts (updated)
Jason Woltje
5048d9eb01