fix(e2e): open avatar dropdown before clicking logout button

The logout action was moved into a user avatar dropdown in the nav.
The E2E test was clicking the now-hidden button directly.

Refs #35
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/e2e/auth.spec.ts

@@ -50,6 +50,8 @@ test.describe('Authentication', () => {
 
 	test('logout clears the session and redirects to /login', async ({ page }) => {
 		await login(page);
+		// Logout is inside the user avatar dropdown — open it first
+		await page.locator('button[aria-haspopup="true"]').click();
 		await page.getByRole('button', { name: 'Abmelden' }).click();
 		await expect(page).toHaveURL(/\/login/);
 		// Confirm session is gone: navigating to / redirects back