feat: AI quiz generation per lesson + hide edit buttons for non-authors

- Generate unique quiz for each lesson using OpenRouter API
- Parse lesson content (TipTap JSON) and send to AI for question generation
- Cache quiz in database to avoid regeneration
- Hide Edit/Delete buttons if current user is not course author
- Add backendUser to auth context for proper authorization checks
- Show certificate button prominently when course is completed

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/app/(dashboard)/dashboard/courses/[id]/page.tsx

@@ -45,13 +45,14 @@ type CourseData = {
   title: string;
   description?: string | null;
   status: string;
+  authorId: string;
   chapters: Chapter[];
 };
 
 export default function CoursePage() {
   const params = useParams();
   const router = useRouter();
-  const { loading: authLoading } = useAuth();
+  const { loading: authLoading, backendUser } = useAuth();
   const id = params?.id as string;
   const [course, setCourse] = useState<CourseData | null>(null);
   const [loading, setLoading] = useState(true);
@@ -248,6 +249,9 @@ export default function CoursePage() {
   const activeLessonMeta = selectedLessonId
     ? flatLessons.find((l) => l.id === selectedLessonId)
     : null;
+  
+  const isAuthor = course && backendUser && course.authorId === backendUser.id;
+  const courseCompleted = completedCount >= totalLessons && totalLessons > 0;
 
   return (
     <div className="flex h-[calc(100vh-4rem)] -m-6 flex-col">
@@ -272,37 +276,51 @@ export default function CoursePage() {
             <div className="h-2 w-2 rounded-full bg-primary" />
             <span className="text-xs font-medium">{progressPercent}% пройдено</span>
           </div>
-          <Button size="sm" variant="outline" asChild>
-            <Link href={`/dashboard/courses/${course.id}/edit`}>
-              <Edit className="mr-1.5 h-3.5 w-3.5" />
-              Редактировать
-            </Link>
-          </Button>
-          <AlertDialog>
-            <AlertDialogTrigger asChild>
-              <Button variant="ghost" size="icon" className="h-8 w-8 text-muted-foreground hover:text-destructive">
-                <Trash2 className="h-4 w-4" />
+          
+          {/* Certificate button - show when course completed */}
+          {courseCompleted && (
+            <Button size="sm" variant="default" onClick={handleGetCertificate} disabled={generatingCertificate}>
+              <GraduationCap className="mr-1.5 h-3.5 w-3.5" />
+              {generatingCertificate ? 'Генерация...' : 'Получить сертификат'}
+            </Button>
+          )}
+          
+          {/* Edit/Delete - only for author */}
+          {isAuthor && (
+            <>
+              <Button size="sm" variant="outline" asChild>
+                <Link href={`/dashboard/courses/${course.id}/edit`}>
+                  <Edit className="mr-1.5 h-3.5 w-3.5" />
+                  Редактировать
+                </Link>
               </Button>
-            </AlertDialogTrigger>
-            <AlertDialogContent>
-              <AlertDialogHeader>
-                <AlertDialogTitle>Удалить курс?</AlertDialogTitle>
-                <AlertDialogDescription>
-                  Курс «{course.title}» будет удалён безвозвратно.
-                </AlertDialogDescription>
-              </AlertDialogHeader>
-              <AlertDialogFooter>
-                <AlertDialogCancel>Отмена</AlertDialogCancel>
-                <AlertDialogAction
-                  onClick={(e) => { e.preventDefault(); handleDelete(); }}
-                  className="bg-destructive text-destructive-foreground hover:bg-destructive/90"
-                  disabled={deleting}
-                >
-                  {deleting ? 'Удаление...' : 'Удалить'}
-                </AlertDialogAction>
-              </AlertDialogFooter>
-            </AlertDialogContent>
-          </AlertDialog>
+              <AlertDialog>
+                <AlertDialogTrigger asChild>
+                  <Button variant="ghost" size="icon" className="h-8 w-8 text-muted-foreground hover:text-destructive">
+                    <Trash2 className="h-4 w-4" />
+                  </Button>
+                </AlertDialogTrigger>
+                <AlertDialogContent>
+                  <AlertDialogHeader>
+                    <AlertDialogTitle>Удалить курс?</AlertDialogTitle>
+                    <AlertDialogDescription>
+                      Курс «{course.title}» будет удалён безвозвратно.
+                    </AlertDialogDescription>
+                  </AlertDialogHeader>
+                  <AlertDialogFooter>
+                    <AlertDialogCancel>Отмена</AlertDialogCancel>
+                    <AlertDialogAction
+                      onClick={(e) => { e.preventDefault(); handleDelete(); }}
+                      className="bg-destructive text-destructive-foreground hover:bg-destructive/90"
+                      disabled={deleting}
+                    >
+                      {deleting ? 'Удаление...' : 'Удалить'}
+                    </AlertDialogAction>
+                  </AlertDialogFooter>
+                </AlertDialogContent>
+              </AlertDialog>
+            </>
+          )}
         </div>
       </div>
 
@@ -520,16 +538,10 @@ export default function CoursePage() {
                   Следующий урок
                   <ChevronRight className="ml-1.5 h-4 w-4" />
                 </Button>
-              ) : completedCount >= totalLessons ? (
-                <Button size="sm" onClick={handleGetCertificate} disabled={generatingCertificate}>
-                  <GraduationCap className="mr-1.5 h-4 w-4" />
-                  {generatingCertificate ? 'Генерация...' : 'Получить сертификат'}
-                </Button>
               ) : (
-                <Button size="sm" variant="outline" disabled>
-                  <GraduationCap className="mr-1.5 h-4 w-4" />
-                  Завершить курс
-                </Button>
+                <div className="text-sm text-muted-foreground">
+                  {courseCompleted ? 'Курс пройден!' : 'Последний урок'}
+                </div>
               )}
             </div>
           </div>