유튜브 api오류 처리 추가

src/pages/Dashboard/DashboardContent.tsx

@@ -571,6 +571,11 @@ const DashboardContent: React.FC<DashboardContentProps> = ({ onNavigate }) => {
             setDashboardData(null);
             return;
           }
+          if (errorData.code === 'YOUTUBE_API_FAILED') {
+            setError({ code: 'YOUTUBE_API_FAILED', message: 'YouTube Analytics API 호출에 실패했습니다.' });
+            setDashboardData(null);
+            return;
+          }
           throw new Error(errorData.detail || `API Error: ${response.status}`);
         }