fix: allow callback route to complete Auth0 code exchange (refs #189)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -557,18 +557,37 @@ function App() {
     );
   }
 
-  // Callback route requires authentication - handled by CallbackPage component
+  if (isCallbackRoute) {
-  if (isCallbackRoute && isAuthenticated) {
+    if (isAuthenticated) {
+      return (
+        <ThemeProvider>
+          <React.Suspense fallback={
+            <div className="flex items-center justify-center min-h-screen">
+              <div className="text-lg">Processing login...</div>
+            </div>
+          }>
+            {mobileMode ? <CallbackMobileScreen /> : <CallbackPage />}
+          </React.Suspense>
+          <DebugInfo />
+        </ThemeProvider>
+      );
+    }
+    if (mobileMode) {
+      return (
+        <ThemeProvider>
+          <Layout mobileMode={true}>
+            <div className="flex items-center justify-center h-64">
+              <div className="text-slate-500">Processing login...</div>
+            </div>
+          </Layout>
+        </ThemeProvider>
+      );
+    }
     return (
       <ThemeProvider>
-        <React.Suspense fallback={
+        <div className="flex items-center justify-center min-h-screen">
-          <div className="flex items-center justify-center min-h-screen">
+          <div className="text-lg">Processing login...</div>
-            <div className="text-lg">Processing login...</div>
+        </div>
-          </div>
-        }>
-          {mobileMode ? <CallbackMobileScreen /> : <CallbackPage />}
-        </React.Suspense>
-        <DebugInfo />
       </ThemeProvider>
     );
   }