Update e2e tests and mocks for locale-based routing

- Adjusted assertions and navigation tests to include `/en` locale prefix for consistency.
- Updated next-intl and components-i18n mocks to support locale handling in tests.
- Renamed "Components" link and related references to "Design System" in homepage tests.
- Disabled typing delay in debounce test for improved test reliability.

frontend/e2e/admin-access.spec.ts

@@ -31,7 +31,7 @@ test.describe('Admin Access Control', () => {
     await page.goto('/en/admin');
 
     // Should be redirected away from admin (to login or home)
-    await page.waitForURL(/\/en\/(auth\/login|$)/);
+    await page.waitForURL(/\/en(\/login)?$/);
     expect(page.url()).not.toContain('/admin');
   });