Doubles frontend test findBy* timeouts to reduce CI flakiness

5000ms was occasionally too tight on the self-hosted Actions runner for
lazy-loaded routes gated behind an async setup-status check (observed on
SettingsPage.test.tsx, passed reliably locally). Bumps to 10000ms across all
nine test files using that pattern, and raises vite.config.ts's global
testTimeout from 15000 to 20000 to keep headroom above it.

frontend/src/pages/AccessDeniedPage.test.tsx

@@ -12,21 +12,21 @@ describe('AccessDeniedPage', () => {
     it('renders the 403 title and message', async () => {
         renderApp('/403');
 
-        expect(await screen.findByTestId('access-denied-title', {}, { timeout: 5000 })).toBeInTheDocument();
+        expect(await screen.findByTestId('access-denied-title', {}, { timeout: 10000 })).toBeInTheDocument();
         expect(screen.getByTestId('access-denied-message')).toBeInTheDocument();
     });
 
     it('renders the back to dashboard button', async () => {
         renderApp('/403');
 
-        expect(await screen.findByTestId('access-denied-back-button', {}, { timeout: 5000 })).toBeInTheDocument();
+        expect(await screen.findByTestId('access-denied-back-button', {}, { timeout: 10000 })).toBeInTheDocument();
     });
 
     it('navigates to login when back button is clicked as guest', async () => {
         mockGuest();
         renderApp('/403');
 
-        const button = await screen.findByTestId('access-denied-back-button', {}, { timeout: 5000 });
+        const button = await screen.findByTestId('access-denied-back-button', {}, { timeout: 10000 });
         await userEvent.click(button);
 
         expect(await screen.findByTestId('login-form-submit-button')).toBeInTheDocument();