feat: P2-12 Teacher profile/workspace + P2-13 Multi-class comparison

P2-12 Teacher Management:
- Add profile JSON field (subjects, joinedAt, qualifications) to User entity
- Add GET/PUT /rbac/users/:id/profile endpoints with UpdateProfileDto
- Add GET /rbac/teacher-workspace endpoint returning assignedClasses,
  todaySchedules, and myStudents
- Create /teacher-workspace page with tabs (My Classes, Today's Schedule,
  My Students)
- Add route with PermissionRoute and menu item in MainLayout

P2-13 Student Archive Multi-class:
- Add GET /students/:id/compare-classes endpoint returning side-by-side
  enrollment data with per-class attendance statistics
- Students module now includes ClassStudent and AttendanceRecord entities
- No 2-enrollment cap existed in the codebase; student enrollments
  already return all records via class-student table

apps/admin/src/App.tsx

@@ -24,6 +24,7 @@ import SchedulesPage from './pages/Schedules';
 import RolesPage from './pages/Roles';
 import PermissionsPage from './pages/Permissions';
 import AttendancePage from './pages/Attendance';
+import TeacherWorkspacePage from './pages/TeacherWorkspace';
 import PermissionRoute from './components/PermissionRoute';
 
 const PrivateRoute: React.FC<{ children: React.ReactNode }> = ({ children }) => {
@@ -220,6 +221,15 @@ const App: React.FC = () => {
                   </PermissionRoute>
                 }
               />
+
+              <Route
+                path="teacher-workspace"
+                element={
+                  <PermissionRoute permission="class:view">
+                    <TeacherWorkspacePage />
+                  </PermissionRoute>
+                }
+              />
             </Route>
           </Routes>
         </BrowserRouter>