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/session-auth.test.ts

@@ -38,6 +38,18 @@ describe('session auth', () => {
     expect(isPublicApiRequest('GET', '/api/v1/attendees')).toBe(false);
   });
 
+  it('classifies absence notification endpoints as public (token-based)', () => {
+    expect(isPublicApiRequest('GET', '/api/v1/classes/absence?token=abc')).toBe(true);
+    expect(isPublicApiRequest('POST', '/api/v1/classes/notify-absence')).toBe(true);
+    // Las rutas autenticadas de clases siguen protegidas.
+    expect(isPublicApiRequest('GET', '/api/v1/classes/today')).toBe(false);
+    expect(isPublicApiRequest('GET', '/api/v1/classes/session-1/students')).toBe(false);
+    expect(isPublicApiRequest('POST', '/api/v1/classes/session-1/attendance')).toBe(false);
+    expect(
+      isPublicApiRequest('POST', '/api/v1/classes/session-1/notify-absence'),
+    ).toBe(false);
+  });
+
   it('allows public requests without a session', async () => {
     const app = new Hono();
     app.use('*', sessionAuthMiddleware);