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);
@@ -249,6 +250,9 @@ export default function CoursePage() {
     ? 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">
       {/* Top bar */}
@@ -272,6 +276,18 @@ export default function CoursePage() {
             <div className="h-2 w-2 rounded-full bg-primary" />
             <span className="text-xs font-medium">{progressPercent}% пройдено</span>
           </div>
+          
+          {/* 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" />
@@ -303,6 +319,8 @@ export default function CoursePage() {
                   </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>

apps/web/src/contexts/auth-context.tsx

@@ -6,8 +6,17 @@ import { getSupabase } from '@/lib/supabase';
 import { useRouter } from 'next/navigation';
 import { api, setApiToken } from '@/lib/api';
 
+interface BackendUser {
+  id: string;
+  email: string;
+  name: string | null;
+  avatarUrl: string | null;
+  subscriptionTier: string;
+}
+
 interface AuthContextType {
   user: User | null;
+  backendUser: BackendUser | null;
   session: Session | null;
   loading: boolean;
   signUp: (email: string, password: string, name: string) => Promise<{ error: Error | null }>;
@@ -20,6 +29,7 @@ const AuthContext = createContext<AuthContextType | undefined>(undefined);
 
 export function AuthProvider({ children }: { children: React.ReactNode }) {
   const [user, setUser] = useState<User | null>(null);
+  const [backendUser, setBackendUser] = useState<BackendUser | null>(null);
   const [session, setSession] = useState<Session | null>(null);
   const [loading, setLoading] = useState(true);
   const router = useRouter();
@@ -64,8 +74,9 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
     const tryExchange = () => {
       api
         .exchangeToken(session.access_token)
-        .then(({ accessToken }) => {
+        .then(({ accessToken, user: backendUserData }) => {
           setApiToken(accessToken);
+          setBackendUser(backendUserData);
           setLoading(false);
         })
         .catch(() => {
@@ -152,6 +163,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
     <AuthContext.Provider
       value={{
         user,
+        backendUser,
         session,
         loading,
         signUp,