test(e2e): add GA4 tracking, mobile, user journey tests and update visual baselines

- Add GA4 event tracking E2E tests (4 cases: page view, form submit, button click, product page)
- Add mobile-specific E2E tests (16 cases: navigation, form, product browsing)
- Add user journey tests (UJ-01: homepage to contact, UJ-02: product discovery)
- Fix E2E test selectors and assertions for consistency
- Update visual regression baselines across all browsers (chromium/firefox/webkit)
- Update Playwright config for new test files

e2e/footer-beian-verify.spec.ts

@@ -1,6 +1,6 @@
 import { test, expect } from '@playwright/test';
 
-test.describe('Footer ICP/Police BeiAn Visibility', () => {
+test.describe('Footer ICP/Police BeiAn Visibility', { tag: '@regression' }, () => {
   test('desktop: ICP and police bei an should be visible', async ({ page }) => {
     await page.setViewportSize({ width: 1440, height: 900 });
     await page.goto('/');