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/server/src/students/students.controller.ts

@@ -280,4 +280,10 @@ export class StudentsController {
     });
     return result;
   }
+
+  @Get(':id/compare-classes')
+  @RequirePermission('student:view')
+  compareClasses(@Param('id') id: string) {
+    return this.service.compareClasses(+id);
+  }
 }