Fix flaky logout test by waiting for navigation

The dispatchEvent('click') on Sign Out triggers a navigation. Wait
for it to complete before checking for the Sign In link.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/e2e/utils.ts

@@ -12,5 +12,6 @@ export async function login(page: Page) {
 
 export async function logout(page: Page) {
   await page.getByText('Sign Out').dispatchEvent('click');
+  await page.waitForURL('**/');
   await expect(page.getByRole('link', {name: 'Sign In'})).toBeVisible();
 }