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/tests/components/admin/users/UserListTable.test.tsx

@@ -161,14 +161,14 @@ describe('UserListTable', () => {
     });
 
     it('calls onSearch after debounce delay', async () => {
-      const user = userEvent.setup();
+      const user = userEvent.setup({ delay: null }); // Disable typing delay for debounce test
       render(<UserListTable {...defaultProps} />);
 
       const searchInput = screen.getByPlaceholderText('Search by name or email...');
 
       await user.type(searchInput, 'alice');
 
-      // Should not call immediately
+      // Should not call immediately (debounce is 300ms)
       expect(defaultProps.onSearch).not.toHaveBeenCalled();
 
       // Should call after debounce (300ms)