feat: add absence notification and analytics features

- Implemented AbsenceNotifyView for notifying absence with session details.
- Created AnalyticsView for displaying group analytics and managing students at risk.
- Added ClassAttendanceView for marking attendance in classes.
- Defined new schemas for analytics and attendance in shared package.

apps/backend/test/attendees.test.ts

@@ -27,6 +27,7 @@ const attendee = {
   guardianName: 'Luis Pérez',
   guardianPhone: null,
   notes: null,
+  notifyToken: null,
   createdAt: new Date('2026-08-01T10:00:00.000Z'),
   updatedAt: new Date('2026-08-01T10:00:00.000Z'),
 };