Harden published curriculum and student flows

apps/student_app/lib/presentation/screens/virtual_labs/labs_registry.dart

@@ -368,7 +368,9 @@ class Grade10LabsRegistry {
 
   /// Whether to surface draft / unreleased virtual labs for local inspection and review.
   /// Defaults to true in development so that the reviewer/teacher can immediately test the labs.
-  static bool previewModeEnabled = true;
+  // Student builds must show released labs only. Draft previews stay available
+  // through explicit authoring/review tooling, never through the student flow.
+  static bool previewModeEnabled = false;
 
   /// Exact identity lookup strictly isolated per subject.
   /// When [previewModeEnabled] is active or [allowPreview] is true, returns the lab for testing.

apps/student_app/lib/presentation/screens/virtual_labs/subject_virtual_labs_view.dart

@@ -126,9 +126,6 @@ class _SubjectVirtualLabsViewState extends State<SubjectVirtualLabsView> {
     final labs = candidateLabs;
 
     if (labs.isEmpty) {
-      if (widget.specializedToolWidget != null) {
-        return widget.specializedToolWidget!;
-      }
       return Center(
         child: Padding(
           padding: const EdgeInsets.all(32),
@@ -154,16 +151,6 @@ class _SubjectVirtualLabsViewState extends State<SubjectVirtualLabsView> {
                     color: Color(0xFF94A3B8), fontSize: 11.5, height: 1.6),
               ),
               const SizedBox(height: 14),
-              TextButton.icon(
-                onPressed: () => _openGallery(context),
-                icon: const Icon(CupertinoIcons.square_grid_2x2, size: 16),
-                label: const Text('معرض المعاينة التأليفية',
-                    style:
-                        TextStyle(fontWeight: FontWeight.w800, fontSize: 12.5)),
-                style: TextButton.styleFrom(
-                  foregroundColor: AppColors.saqelCyan,
-                ),
-              ),
             ],
           ),
         ),