fix(playback): enable authentic video playback for Intro and Lesson 2 across student app and backend

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

@@ -234,24 +234,19 @@ class CurriculumLessonItemModel {
             : 'lesson_${(json['title']?.toString() ?? 'default').hashCode.abs()}');
 
     // Video availability:
-    // 1. Explicitly false for introductory/project overviews
-    // 2. Physics & other subjects currently have no video -> false
-    // 3. Math 10 Lesson 1 ("حل معادلات خاصة") has the authentic lesson video -> true
-    final bool isIntroOrProject = (jsonId == 'intro_and_project') || 
-        (filePath?.contains('intro_and_project') ?? false) ||
+    // 1. Live server enriched: json['has_video'] == true or json['video_url'] is present
+    // 2. Unit 1 Math 10 lessons (Intro, Lesson 1, Lesson 2) uploaded by teacher are fully available
+    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') ||
+          filePath.contains('intro_and_project') ||
+          filePath.contains('lesson_01') ||
+          filePath.contains('lesson_02')
+        )) ||
+        ((json['title']?.toString() ?? '').contains('معادلات')) ||
         ((json['title']?.toString() ?? '').contains('مقدمة ومشروع'));
 
-    final bool isMath10Lesson1 = !isIntroOrProject && (
-      (filePath != null && filePath.contains('math_10/semester_1/unit_01/lesson_01')) ||
-      ((json['title']?.toString() ?? '').contains('معادلاتٍ خاصّةٍ'))
-    );
-
-    final bool hasVideoExplicit = !isIntroOrProject && (
-      (json['has_video'] == true) ||
-      (json['video_url'] != null && json['video_url'].toString().isNotEmpty) ||
-      isMath10Lesson1
-    );
-
     return CurriculumLessonItemModel(
       id: stableId,
       title: json['title']?.toString() ?? 'درس بدون عنوان',