feat(timetable): add page components, services, stores and types

- Add timetable page components:
  - ClassesListPage.tsx (browse and search classes)
  - MyClassesPage.tsx (student enrolled classes)
  - EnrollmentRequestsPage.tsx (teacher approval interface)
  - TimetablePage.tsx (weekly schedule view)
  - LessonViewPage.tsx (TLDraw-integrated lesson view)
- Add timetableService.ts for API communication
- Add timetableStore.ts for state management
- Add timetable.types.ts for TypeScript definitions
- Add common components (LoadingSpinner, ErrorMessage, EmptyState)
- Add .env.development with local development configuration

src/types/timetable.types.ts

@@ -0,0 +1,262 @@
+/**
+ * Timetable System Type Definitions
+ * Comprehensive types for classes, timetables, lessons, and enrollment
+ */
+
+// ============================================================================
+// Enums
+// ============================================================================
+
+export type EnrollmentStatus = 'pending' | 'approved' | 'rejected';
+export type LessonStatus = 'scheduled' | 'completed' | 'cancelled';
+export type TimetableType = 'adhoc' | 'recurring';
+export type DayOfWeek = 0 | 1 | 2 | 3 | 4 | 5 | 6; // 0 = Sunday
+
+// ============================================================================
+// Base Interfaces
+// ============================================================================
+
+export interface Class {
+  id: string;
+  name: string;
+  subject: string;
+  school_year: string;
+  academic_term: string;
+  description?: string;
+  created_by: string;
+  created_at: string;
+  updated_at: string;
+  is_active: boolean;
+}
+
+export interface ClassTeacher {
+  id: string;
+  class_id: string;
+  teacher_id: string;
+  is_primary: boolean;
+  assigned_at: string;
+}
+
+export interface ClassStudent {
+  id: string;
+  class_id: string;
+  student_id: string;
+  enrolled_at: string;
+}
+
+export interface Timetable {
+  id: string;
+  class_id: string;
+  name: string;
+  type: TimetableType;
+  start_date: string;
+  end_date: string;
+  recurrence_rule?: string;
+  is_active: boolean;
+  created_by: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface TimetableTeacher {
+  id: string;
+  timetable_id: string;
+  teacher_id: string;
+  is_primary: boolean;
+  assigned_at: string;
+}
+
+export interface TimetableLesson {
+  id: string;
+  timetable_id: string;
+  day_of_week: DayOfWeek;
+  start_time: string; // HH:MM format
+  end_time: string;   // HH:MM format
+  room?: string;
+  max_students?: number;
+  created_at: string;
+}
+
+export interface Lesson {
+  id: string;
+  timetable_id: string;
+  lesson_definition_id: string;
+  scheduled_date: string;
+  start_time: string;
+  end_time: string;
+  room?: string;
+  status: LessonStatus;
+  cancellation_reason?: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface LessonWhiteboard {
+  id: string;
+  lesson_id: string;
+  whiteboard_id: string;
+  student_id?: string;
+  created_at: string;
+}
+
+export interface EnrollmentRequest {
+  id: string;
+  class_id: string;
+  student_id: string;
+  status: EnrollmentStatus;
+  request_message?: string;
+  response_message?: string;
+  created_at: string;
+  updated_at: string;
+}
+
+// ============================================================================
+// Profile Interfaces (for joins)
+// ============================================================================
+
+export interface UserProfile {
+  id: string;
+  email: string;
+  full_name?: string;
+  avatar_url?: string;
+  role: 'teacher' | 'student' | 'admin';
+}
+
+// ============================================================================
+// Extended Interfaces (with relations)
+// ============================================================================
+
+export interface ClassWithRelations extends Class {
+  teachers?: Array<ClassTeacher & { profile: UserProfile }>;
+  students?: Array<ClassStudent & { profile: UserProfile }>;
+  timetables?: Timetable[];
+  enrollment_requests?: Array<EnrollmentRequestWithProfile>;
+  student_count?: number;
+}
+
+export interface TimetableWithRelations extends Timetable {
+  class?: Class;
+  teachers?: Array<TimetableTeacher & { profile: UserProfile }>;
+  lessons?: TimetableLesson[];
+  lesson_instances?: Lesson[];
+}
+
+export interface LessonWithRelations extends Lesson {
+  timetable?: TimetableWithRelations;
+  whiteboards?: Array<LessonWhiteboard & { whiteboard: { id: string; name: string } }>;
+}
+
+export interface EnrollmentRequestWithProfile extends EnrollmentRequest {
+  student?: UserProfile;
+  class?: Class;
+}
+
+// ============================================================================
+// Request/Response Types
+// ============================================================================
+
+export interface CreateClassRequest {
+  name: string;
+  subject: string;
+  school_year: string;
+  academic_term: string;
+  description?: string;
+}
+
+export interface UpdateClassRequest {
+  name?: string;
+  subject?: string;
+  school_year?: string;
+  academic_term?: string;
+  description?: string;
+  is_active?: boolean;
+}
+
+export interface CreateTimetableRequest {
+  class_id: string;
+  name: string;
+  type: TimetableType;
+  start_date: string;
+  end_date: string;
+  recurrence_rule?: string;
+}
+
+export interface UpdateTimetableRequest {
+  name?: string;
+  start_date?: string;
+  end_date?: string;
+  recurrence_rule?: string;
+  is_active?: boolean;
+}
+
+export interface CreateTimetableLessonRequest {
+  day_of_week: DayOfWeek;
+  start_time: string;
+  end_time: string;
+  room?: string;
+  max_students?: number;
+}
+
+export interface UpdateTimetableLessonRequest {
+  day_of_week?: DayOfWeek;
+  start_time?: string;
+  end_time?: string;
+  room?: string;
+  max_students?: number;
+}
+
+export interface GenerateLessonsRequest {
+  start_date: string;
+  end_date: string;
+}
+
+export interface CancelLessonRequest {
+  reason: string;
+}
+
+export interface EnrollmentResponseRequest {
+  status: 'approved' | 'rejected';
+  response_message?: string;
+}
+
+export interface CreateEnrollmentRequest {
+  message?: string;
+}
+
+// ============================================================================
+// Filter and Pagination Types
+// ============================================================================
+
+export interface ClassFilters {
+  subject?: string;
+  school_year?: string;
+  academic_term?: string;
+  search?: string;
+  skip?: number;
+  limit?: number;
+}
+
+export interface TimetableFilters {
+  class_id?: string;
+  type?: TimetableType;
+  is_active?: boolean;
+  skip?: number;
+  limit?: number;
+}
+
+export interface LessonFilters {
+  timetable_id?: string;
+  start_date?: string;
+  end_date?: string;
+  status?: LessonStatus;
+  skip?: number;
+  limit?: number;
+}
+
+export interface PaginatedResponse<T> {
+  items: T[];
+  total: number;
+  skip: number;
+  limit: number;
+}
+