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

apps/student_app/lib/data/models/socratic_checkpoint_model.dart

@@ -79,6 +79,7 @@ class SocraticOptionModel {
 /// Model for Lesson Playback Data (Streams, Versions, Chapters, Checkpoints)
 class LessonPlaybackData {
   final int lessonId;
+  final String? videoVersionId;
   final String title;
   final int durationSeconds;
   final String videoUrl;
@@ -89,6 +90,7 @@ class LessonPlaybackData {
 
   const LessonPlaybackData({
     required this.lessonId,
+    this.videoVersionId,
     required this.title,
     required this.durationSeconds,
     required this.videoUrl,
@@ -129,9 +131,10 @@ class LessonPlaybackData {
     final lastPos = (json['last_position_seconds'] ?? playback['last_position_seconds'] ?? json['progress']?['position_seconds']) as num?;
 
     return LessonPlaybackData(
-      lessonId: (lesson['id'] as num?)?.toInt() ?? 0,
-      title: lesson['title']?.toString() ?? 'الدرس التفاعلي',
-      durationSeconds: (lesson['duration_seconds'] as num?)?.toInt() ?? 0,
+      lessonId: (lesson['id'] as num?)?.toInt() ?? (json['lesson_id'] as num?)?.toInt() ?? 0,
+      videoVersionId: json['video_version_id']?.toString(),
+      title: lesson['title']?.toString() ?? json['title']?.toString() ?? 'الدرس التفاعلي',
+      durationSeconds: (lesson['duration_seconds'] as num?)?.toInt() ?? (json['duration_seconds'] as num?)?.toInt() ?? 0,
       videoUrl: vidUrl,
       storageType: playback['storage_type']?.toString() ?? 'api_upload',
       availableVersions: versions,
@@ -142,6 +145,7 @@ class LessonPlaybackData {
 
   LessonPlaybackData copyWith({
     int? lessonId,
+    String? videoVersionId,
     String? title,
     int? durationSeconds,
     String? videoUrl,
@@ -152,6 +156,7 @@ class LessonPlaybackData {
   }) {
     return LessonPlaybackData(
       lessonId: lessonId ?? this.lessonId,
+      videoVersionId: videoVersionId ?? this.videoVersionId,
       title: title ?? this.title,
       durationSeconds: durationSeconds ?? this.durationSeconds,
       videoUrl: videoUrl ?? this.videoUrl,