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

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

@@ -30,7 +30,7 @@ class SubjectModel {
     this.stream = 'scientific',
     this.totalUnits = 0,
     this.totalLessons = 0,
-    this.masteryScore = 85.0,
+    this.masteryScore = 0,
     this.units = const [],
     this.textbooks = const [],
     this.worksheets = const [],
@@ -95,7 +95,7 @@ class SubjectModel {
       stream: json['stream']?.toString() ?? 'scientific',
       totalUnits: parsedUnits.isNotEmpty ? parsedUnits.length : styling.defaultUnits,
       totalLessons: parsedUnits.fold(0, (sum, u) => sum + u.lessons.length),
-      masteryScore: (json['mastery_score'] as num?)?.toDouble() ?? 88.0,
+      masteryScore: (json['mastery_score'] as num?)?.toDouble() ?? 0,
       units: parsedUnits,
       textbooks: parsedTextbooks,
       worksheets: parsedWorksheets,
@@ -198,6 +198,7 @@ class CurriculumLessonItemModel {
   final String title;
   final List<String> outcomes;
   final String? markdownFilePath;
+  final String? curriculumLessonId;
   final int durationSeconds;
   final int checkpointsCount;
   final bool isCompleted;
@@ -208,8 +209,9 @@ class CurriculumLessonItemModel {
     required this.title,
     this.outcomes = const [],
     this.markdownFilePath,
-    this.durationSeconds = 1200, // 20 mins default
-    this.checkpointsCount = 3,
+    this.curriculumLessonId,
+    this.durationSeconds = 0,
+    this.checkpointsCount = 0,
     this.isCompleted = false,
     this.hasVideo = false,
   });
@@ -233,24 +235,17 @@ class CurriculumLessonItemModel {
             ? filePath.replaceAll(RegExp(r'[^a-zA-Z0-9_]'), '_')
             : 'lesson_${(json['title']?.toString() ?? 'default').hashCode.abs()}');
 
-    // Video availability:
-    // 1. Live server enriched: json['has_video'] == true or json['video_url'] is present
-    // 2. Exact uploaded lessons in Grade 10 Math Unit 1 (Intro, Lesson 1, Lesson 2)
-    final bool hasVideoExplicit = (json['has_video'] == true) ||
-        (json['video_url'] != null && json['video_url'].toString().isNotEmpty) ||
-        (filePath != null && (
-          filePath.contains('math_10/semester_1/unit_01/intro_and_project') ||
-          filePath.contains('math_10/semester_1/unit_01/lesson_01') ||
-          filePath.contains('math_10/semester_1/unit_01/lesson_02')
-        ));
+    // Only the server may declare a published lesson playable.
+    final bool hasVideoExplicit = json['has_video'] == true;
 
     return CurriculumLessonItemModel(
       id: stableId,
       title: json['title']?.toString() ?? 'درس بدون عنوان',
       outcomes: outs,
       markdownFilePath: filePath,
-      durationSeconds: (json['duration_seconds'] as num?)?.toInt() ?? 1200,
-      checkpointsCount: (json['checkpoints_count'] as num?)?.toInt() ?? 3,
+      curriculumLessonId: json['curriculum_lesson_id']?.toString(),
+      durationSeconds: (json['duration_seconds'] as num?)?.toInt() ?? 0,
+      checkpointsCount: (json['checkpoints_count'] as num?)?.toInt() ?? 0,
       isCompleted: (json['is_completed'] as bool?) ?? false,
       hasVideo: hasVideoExplicit,
     );