fixed frontent test errors

frontend/vue-app/src/components/shared/__tests__/LoginButton.spec.ts

@@ -4,6 +4,10 @@ import { nextTick } from 'vue'
 import LoginButton from '../LoginButton.vue'
 import { authenticateParent, logoutParent } from '../../../stores/auth'
 
+vi.mock('vue-router', () => ({
+  useRouter: vi.fn(() => ({ push: vi.fn() })),
+}))
+
 // Mock imageCache module
 vi.mock('@/common/imageCache', () => ({
   getCachedImageUrl: vi.fn(async (imageId: string) => `blob:mock-url-${imageId}`),