Implement verified curriculum, video review, watch sessions, ledger safeguards, and remove demo data

apps/student_app/lib/logic/cubits/video_playback_cubit.dart

@@ -71,6 +71,9 @@ class VideoPlaybackError extends VideoPlaybackState {
 class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
   final CurriculumRepository _repo;
   int _lastObservedPosition = -1;
+  String? _watchSessionId;
+  int _watchSequence = 1;
+  int _lastWatchEventPosition = 0;
 
   VideoPlaybackCubit({CurriculumRepository? repo})
       : _repo = repo ?? CurriculumRepository(),
@@ -86,19 +89,30 @@ class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
     return fallbackId ?? 'lesson_default';
   }
 
-  Future<void> loadLesson(CurriculumLessonItemModel lesson, {SubjectModel? subject}) async {
+  Future<void> loadLesson(CurriculumLessonItemModel lesson, {SubjectModel? subject, String? selectedVideoVersionId}) async {
     AppLogger.log('Loading Socratic playback for lesson: ${lesson.title}', tag: 'VIDEO_CUBIT');
     _lastObservedPosition = -1;
     emit(VideoPlaybackLoading());
     final storageKey = _getLessonStorageKey(lesson);
 
     try {
-      final cleanKey = (lesson.markdownFilePath ?? lesson.id).replaceAll(RegExp(r'\.md$'), '');
-      var playback = await _repo.getLessonPlayback(cleanKey, subjectId: subject?.id, title: lesson.title);
+      final versionId = lesson.curriculumLessonId;
+      if (versionId == null || versionId.isEmpty) {
+        throw StateError('هذا الدرس غير منشور بعد ضمن حزمة المحتوى المعتمدة.');
+      }
+      final published = await _repo.getPublishedLessonVideos(versionId);
+      if (published.isEmpty) throw StateError('لا توجد حصة منشورة ومصرح بها لهذا الدرس بعد.');
+      // Selection is performed in the lesson screen when several teachers exist.
+      var playback = await _repo.getVideoVersionPlayback(selectedVideoVersionId ?? published.first.videoVersionId);
       if (playback.videoUrl.isEmpty) {
         throw StateError('لم يربط الخادم فيديو R2 بهذا الدرس بعد.');
       }
       
+      _watchSessionId = null; _watchSequence = 1; _lastWatchEventPosition = 0;
+      if (playback.videoVersionId != null && playback.videoVersionId!.isNotEmpty) {
+        try { _watchSessionId = await _repo.startWatchSession(playback.videoVersionId!); } catch (_) {}
+      }
+
       // Load saved resume position strictly per video
       int resumePos = playback.lastPositionSeconds ?? 0;
       Set<int> passedIds = {};
@@ -151,6 +165,13 @@ class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
     }
   }
 
+  Future<void> endWatchSession() async {
+    final session = _watchSessionId;
+    if (session == null) return;
+    _watchSessionId = null;
+    try { await _repo.recordWatchEvent(session, ++_watchSequence, 'end', _lastObservedPosition.clamp(0, 1 << 31) * 1000); } catch (_) {}
+  }
+
   void togglePlayPause() {
     final currentState = state;
     if (currentState is VideoPlaybackReady && currentState.activeCheckpoint == null) {
@@ -197,11 +218,11 @@ class VideoPlaybackCubit extends Cubit<VideoPlaybackState> {
         );
       }
       if (currentState.playbackData.lessonId > 0) {
-        await _repo.saveProgress(
-          lessonId: currentState.playbackData.lessonId,
-          positionSeconds: positionSeconds,
-          watchedSeconds: watchedSeconds,
-        );
+        await _repo.saveProgress(lessonId: currentState.playbackData.lessonId, positionSeconds: positionSeconds, watchedSeconds: watchedSeconds);
+      }
+      if (_watchSessionId != null && positionSeconds - _lastWatchEventPosition >= 30) {
+        _watchSequence++; _lastWatchEventPosition = positionSeconds;
+        await _repo.recordWatchEvent(_watchSessionId!, _watchSequence, 'heartbeat', positionSeconds * 1000);
       }
     } catch (e) {
       AppLogger.log('Progress sync deferred: $e', tag: 'VIDEO_CUBIT');