Fix admin login and CORS issues

- Update CORS configuration to allow frontend on port 3005
- Fix auth service to map email field to username for backend compatibility
- Add loading state handling in AdminLayout
- Add error boundary to dashboard route
- Fix unused parameter warning in login function

🤖 Generated with [Claude Code](https://claude.ai/code)

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

frontend/src/contexts/AdminAuthContext.tsx

@@ -35,15 +35,21 @@ export const AdminAuthProvider: React.FC<AdminAuthProviderProps> = ({ children }
 
   useEffect(() => {
     // Check if user has a valid token on mount
-    const token = getAuthToken(true);
-    if (token) {
-      // TODO: Validate token with backend and get user info
-      setIsAuthenticated(true);
-    }
-    setIsLoading(false);
+    const checkAuth = async () => {
+      const token = getAuthToken(true);
+      if (token) {
+        // For now, just assume the token is valid
+        // TODO: Validate token with backend and get user info
+        setIsAuthenticated(true);
+      }
+      setIsLoading(false);
+    };
+    
+    checkAuth();
   }, []);
 
   const login = (_token: string, user: AdminUser) => {
+    // Token is already stored in cookie by authService
     setUser(user);
     setIsAuthenticated(true);
     setError(null);