feat: add course catalog, enrollment, progress tracking, quizzes, and reviews

Backend changes:
- Add Enrollment and LessonProgress models to track user progress
- Add UserRole enum (USER, MODERATOR, ADMIN)
- Add course verification and moderation fields
- New CatalogModule: public course browsing, publishing, verification
- New EnrollmentModule: enroll, progress tracking, quiz submission, reviews
- Add quiz generation endpoint to LessonsController

Frontend changes:
- Redesign course viewer: proper course UI with lesson navigation, progress bar
- Add beautiful typography styles for course content (prose-course)
- Fix first-login bug with token exchange retry logic
- New pages: /catalog (public courses), /catalog/[id] (course details), /learning (enrollments)
- Add LessonQuiz component with scoring and results
- Update sidebar navigation: add Catalog and My Learning links
- Add publish/verify buttons in course editor
- Integrate enrollment progress tracking with backend

All courses now support: sequential progression, quiz tests, reviews, ratings,
author verification badges, and full marketplace publishing workflow.

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

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

@@ -57,16 +57,30 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
       setApiToken(null);
       return;
     }
-    api
-      .exchangeToken(session.access_token)
-      .then(({ accessToken }) => {
-        setApiToken(accessToken);
-        setLoading(false);
-      })
-      .catch(() => {
-        setApiToken(null);
-        setLoading(false);
-      });
+
+    let attempt = 0;
+    const maxRetries = 3;
+
+    const tryExchange = () => {
+      api
+        .exchangeToken(session.access_token)
+        .then(({ accessToken }) => {
+          setApiToken(accessToken);
+          setLoading(false);
+        })
+        .catch(() => {
+          attempt++;
+          if (attempt < maxRetries) {
+            // Retry with exponential backoff (500ms, 1500ms, 3500ms)
+            setTimeout(tryExchange, 500 * Math.pow(2, attempt));
+          } else {
+            setApiToken(null);
+            setLoading(false);
+          }
+        });
+    };
+
+    tryExchange();
   }, [session?.access_token]);
 
   // Exchange Supabase token for backend JWT; keep loading true until done so API calls wait for JWT