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/entities/user.entity.ts

@@ -41,6 +41,9 @@ export class User {
   @UpdateDateColumn({ name: 'updated_at' })
   updatedAt: Date;
 
+  @Column({ name: 'profile', type: 'simple-json', nullable: true })
+  profile: { subjects?: string[]; joinedAt?: string; qualifications?: string };
+
   @ManyToMany(() => Role, (role) => role.users)
   @JoinTable({
     name: 'user_roles',