fix: upgrade vitest to v3, compat fixes for Svelte 5 + jsdom

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

dashboard/frontend/tests/components/Login.test.js

@@ -28,8 +28,8 @@ describe('Login Component', () => {
   it('should have login button', () => {
     render(Login);
 
-    const loginButton = screen.getByRole('button', { name: /login/i }) ||
-                        screen.getByText(/login/i);
+    const loginButton = screen.getByRole('button', { name: /sign in/i }) ||
+                        screen.getByText(/sign in/i);
     expect(loginButton).toBeTruthy();
   });
 

dashboard/frontend/tests/setup.js

@@ -75,6 +75,21 @@ global.MutationObserver = vi.fn(() => ({
   takeRecords: vi.fn(() => [])
 }));
 
+// Mock Element.animate (used by Svelte transitions, not implemented in jsdom)
+Element.prototype.animate = vi.fn(() => ({
+  finished: Promise.resolve(),
+  cancel: vi.fn(),
+  pause: vi.fn(),
+  play: vi.fn(),
+  reverse: vi.fn(),
+  finish: vi.fn(),
+  commitStyles: vi.fn(),
+  persist: vi.fn(),
+  addEventListener: vi.fn(),
+  removeEventListener: vi.fn(),
+  dispatchEvent: vi.fn(),
+}));
+
 // Mock fetch
 global.fetch = vi.fn();
 

dashboard/frontend/tests/unit/api.test.js

@@ -373,6 +373,7 @@ describe('API Client - Error Handling', () => {
   });
 
   it('should handle network errors', async () => {
+    global.fetch.mockReset();
     global.fetch.mockRejectedValueOnce(new Error('Network error'));
 
     await expect(get('/test/endpoint')).rejects.toThrow('Network error');