feat: remove published status check when deleting lessons

Remove validation that prevented deletion of published lessons. Lessons can now be deleted regardless of their published status without requiring unpublishing first.

Backend/src/services/ChaptersLesson.service.ts

@@ -565,11 +565,6 @@ export class ChaptersLessonService {
 
             if (!lesson) throw new NotFoundError('Lesson not found');
 
-            // Check if lesson is published
-            if (lesson.is_published) {
-                throw new ValidationError('Cannot delete published lesson. Please unpublish first.');
-            }
-
             // Delete attachment files from MinIO
             if (lesson.attachments && lesson.attachments.length > 0) {
                 for (const attachment of lesson.attachments) {