feat: Add daily event notification emails via cron job

- Add node-cron for scheduled tasks
- Create cron/calendar structure with:
  - email-template.js: HTML email template for event notifications
  - event-notifier.js: Logic to query tomorrow's events and send emails
  - index.js: Cron scheduler (runs daily at configurable time)
- Send notifications via JMAP using sender email from database
- Add admin endpoint POST /api/admin/trigger-notifications for testing
- Add env variables: NOTIFICATION_TIME, NOTIFICATION_SENDER_EMAIL

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/routes/admin.routes.js

@@ -57,4 +57,11 @@ router.delete(
 // Server status (CPU, RAM, Disk, Network, Uptime)
 router.get('/server-status', adminController.getServerStatus);
 
+/**
+ * Notifications
+ */
+
+// Manually trigger event notifications (for testing)
+router.post('/trigger-notifications', adminController.triggerNotifications);
+
 export default router;