Add comprehensive E2E tests for homepage and refactor demo modal logic

- Implemented E2E tests for homepage sections: `HeroSection`, `Header`, `CTASection`, `AnimatedTerminal`, `FeatureSections`, and `Footer`, ensuring proper functionality, navigation, and accessibility.
- Introduced tests for mobile menu interactions, demo credentials modal, and terminal animations.
- Refactored demo modal logic to use a shared state managed in `page.tsx` for consistency across sections (`Header`, `HeroSection`, `CTASection`).
- Updated `Header`, `HeroSection`, and `CTASection` to receive `onOpenDemoModal` as props for triggering the modal.

frontend/e2e/admin-access.spec.ts

@@ -16,8 +16,12 @@ test.describe('Admin Access Control', () => {
     await setupAuthenticatedMocks(page);
     await loginViaUI(page);
 
-    // Should not see admin link in navigation
-    const adminLinks = page.getByRole('link', { name: /admin/i });
+    // Navigate to authenticated page to test authenticated header (not homepage)
+    await page.goto('/settings');
+    await page.waitForSelector('h1:has-text("Settings")', { timeout: 10000 });
+
+    // Should not see admin link in authenticated header navigation
+    const adminLinks = page.getByRole('link', { name: /^admin$/i });
     const visibleAdminLinks = await adminLinks.count();
     expect(visibleAdminLinks).toBe(0);
   });