feat: refine integration tests and fix ci stability

- Update Playwright tests for Admin, Auth, Gameplay, and Curator to be more robust.
- Fix Admin login API to support plain text env vars for testing convenience.
- Implement mock Login in Curator page for integration testing.
- Add placeholder for Curator Specials page to resolve build errors.
- Add CSS injection to tests to hide Next.js dev overlays intercepting clicks.
- Improve test selectors and timeouts for better stability in CI/Webkit.

tests/auth.spec.ts

@@ -17,15 +17,22 @@ test.describe('Authentication', () => {
     test('Admin login flow', async ({ page }) => {
         // Navigate to admin login
         await page.goto('/en/admin');
+        await page.addStyleTag({ content: 'nextjs-portal, #nextjs-dev-overlay, [data-nextjs-dev-overlay] { display: none !important; }' });
 
         const passwordInput = page.getByPlaceholder('Password');
+        const usernameInput = page.getByPlaceholder('Username');
 
-        if (await passwordInput.isVisible()) {
-            await passwordInput.fill('admin123');
-            await page.getByRole('button', { name: 'Login' }).click({ force: true });
+        // Admin page should have password input (and maybe username if curator logic is shared, but usually just password)
+        // Adjust based on actual UI. admin/page.tsx has only password.
 
-            // Should now be on admin page
-            await expect(page.getByRole('heading', { name: 'Hördle Admin Dashboard' })).toBeVisible();
-        }
+        page.on('dialog', dialog => console.log(`Dialog message: ${dialog.message()}`));
+
+        await expect(passwordInput).toBeVisible();
+        await passwordInput.fill('admin123');
+        await page.getByRole('button', { name: 'Login' }).dispatchEvent('click');
+        await expect(page).toHaveURL(/\/(admin|en\/admin)/);
+
+        // Should now be on admin page
+        await expect(page.getByRole('heading', { name: 'Hördle Admin Dashboard' })).toBeVisible();
     });
 });