perf: optimize app startup and background lifecycles

tests/unit/login-page.test.tsx

@@ -44,7 +44,7 @@ describe('Login page', () => {
     vi.unstubAllGlobals();
   });
 
-  it('keeps the login route reachable from the app router', () => {
+  it('keeps the login route reachable from the app router', async () => {
     vi.stubGlobal('__NIANCODE_RENDERER_ONLY__', true);
 
     render(
@@ -53,7 +53,7 @@ describe('Login page', () => {
       </MemoryRouter>,
     );
 
-    expect(screen.getByRole('button', { name: '在浏览器中继续' })).toBeInTheDocument();
+    expect(await screen.findByRole('button', { name: '在浏览器中继续' })).toBeInTheDocument();
   });
 
   it('uses Chinese copy and keeps upstream HTML errors concise', () => {