test(admin): sync page tests with component changes (BUG-007)

Fix 6 page test files to match actual component output:
- Login: cookie-based auth login(account), brand text updates
- Config/Logs/Prompts: remove stale description text assertions
- ModelServices: check for actual table buttons instead of title
- Usage: update description text to match PageHeader

All 132 tests pass (17/17 files).

admin-v2/tests/pages/Login.test.tsx

@@ -111,7 +111,7 @@ describe('Login page', () => {
   it('renders the login form with username and password fields', () => {
     renderLogin()
 
-    expect(screen.getByText('登录到 ZCLAW')).toBeInTheDocument()
+    expect(screen.getByText('登录')).toBeInTheDocument()
     expect(screen.getByPlaceholderText('请输入用户名')).toBeInTheDocument()
     expect(screen.getByPlaceholderText('请输入密码')).toBeInTheDocument()
     const submitButton = getSubmitButton()
@@ -121,8 +121,10 @@ describe('Login page', () => {
   it('shows the ZCLAW brand logo', () => {
     renderLogin()
 
-    expect(screen.getByText('Z')).toBeInTheDocument()
-    expect(screen.getByText(/ZCLAW Admin/)).toBeInTheDocument()
+    // "Z" logo appears in both desktop brand panel and mobile-only logo
+    const zElements = screen.getAllByText('Z')
+    expect(zElements.length).toBeGreaterThanOrEqual(1)
+    expect(screen.getByText('AI Agent 管理平台')).toBeInTheDocument()
   })
 
   it('successful login calls authStore.login and navigates to /', async () => {
@@ -136,11 +138,7 @@ describe('Login page', () => {
     await user.click(getSubmitButton())
 
     await waitFor(() => {
-      expect(mockLogin).toHaveBeenCalledWith(
-        'jwt-token-123',
-        'refresh-token-456',
-        mockAccount,
-      )
+      expect(mockLogin).toHaveBeenCalledWith(mockAccount)
     })
 
     expect(mockNavigate).toHaveBeenCalledWith('/', { replace: true })