test(mobile): add mobile E2E test suite (53 tests) and fix layout issues

Add comprehensive mobile testing coverage:
- Add chromium-mobile functional test project (iPhone 14, isMobile, hasTouch)
- Add mobile user journey tests (UJ-01/02/04/05/10 mobile variants)
- Add mobile performance baseline tests (FCP/LCP/load time)
- Add mobile accessibility tests (axe-core WCAG 2.1 AA, touch targets,
  form labels, alt text, contrast)
- Update README with progress and new npm scripts

Fix pre-existing issues:
- Fix footer component layout and test assertions
- Fix admin content page sidebar navigation and breadcrumb
- Fix standalone products page metadata and layout
- Fix product detail/service value sections
- Fix contact form layout on mobile
- Fix navigation constants and products data
- Fix layout.tsx CMS config and theme handling
- Fix erp-upgrade content layout

package.json

@@ -36,6 +36,8 @@
     "test:e2e:standard": "cd e2e && npx playwright test --grep @regression",
     "test:e2e:journey": "cd e2e && npx playwright test --grep @journey",
     "test:e2e:mobile": "cd e2e && npx playwright test --grep @mobile",
+    "test:e2e:mobile:performance": "cd e2e && npx playwright test --grep @mobile.*@performance",
+    "test:e2e:mobile:accessibility": "cd e2e && npx playwright test --grep @mobile.*@accessibility",
     "test:mutation": "rm -rf .stryker-tmp && npx stryker run --inPlace",
     "test:mutation:quick": "rm -rf .stryker-tmp && npx stryker run --inPlace --mutate 'src/lib/utils.ts'",
     "test:all": "npm run type-check && npm run lint && npm run test:coverage && npm run test:e2e:fast && npm run test:security:headers",