test: update playwright script and fix jsdom alert mock

frontend/admin/src/components/common/ui-consistency.test.tsx

@@ -86,6 +86,10 @@ describe('PageHeader Component', () => {
 // =============================================================================
 
 describe('Form Validation Consistency', () => {
+  beforeEach(() => {
+    vi.spyOn(window, 'alert').mockImplementation(() => {})
+  })
+
   it('validates required fields', async () => {
     const user = userEvent.setup()
     const handleSubmit = vi.fn()