feat: downgrade tech stack to stable versions and integrate GA4 error monitoring

- Downgrade Next.js 16→14.2, React 19→18.3, Tailwind 4→3.4
- Add comprehensive GA4 error monitoring system
- Create Jenkins CI/CD pipeline with quality gates
- Fix build issues: ESLint, SWC conflict, config format
- Add documentation for deployment and error tracking

src/components/analytics/CookieConsent.tsx

@@ -48,6 +48,7 @@ export function CookieConsent() {
           necessary: true,
           analytics: legacyConsent === 'granted',
           marketing: false,
+          functionality: true,
           timestamp: Date.now(),
         };
         storePreferences(migratedPrefs);
@@ -91,6 +92,7 @@ export function CookieConsent() {
       necessary: true,
       analytics: true,
       marketing: false,
+      functionality: true,
       timestamp: Date.now(),
     };
     handleSavePreferences(allAccepted);
@@ -102,6 +104,7 @@ export function CookieConsent() {
       necessary: true,
       analytics: false,
       marketing: false,
+      functionality: true,
       timestamp: Date.now(),
     };
     handleSavePreferences(allRejected);