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

package.json

@@ -40,14 +40,16 @@
   "dependencies": {
     "@playwright/test": "^1.58.2",
     "@radix-ui/react-slot": "^1.2.4",
+    "@sentry/nextjs": "^10.52.0",
+    "@sentry/tracing": "^7.120.4",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
     "framer-motion": "^12.34.3",
     "lucide-react": "^0.563.0",
-    "next": "16.1.6",
-    "react": "19.2.3",
-    "react-dom": "19.2.3",
+    "next": "^14.2.21",
+    "react": "^18.3.1",
+    "react-dom": "^18.3.1",
     "tailwind-merge": "^3.4.0",
     "zod": "^4.3.6"
   },
@@ -62,19 +64,19 @@
     "@commitlint/config-conventional": "^20.5.0",
     "@eslint/eslintrc": "^3.3.5",
     "@lhci/cli": "^0.15.1",
-    "@tailwindcss/postcss": "^4",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.2",
     "@testing-library/user-event": "^14.6.1",
     "@types/jest": "^30.0.0",
     "@types/node": "^20",
-    "@types/react": "^19",
-    "@types/react-dom": "^19",
+    "@types/react": "^18",
+    "@types/react-dom": "^18",
     "@typescript-eslint/eslint-plugin": "^8.57.0",
     "@typescript-eslint/parser": "^8.57.0",
+    "autoprefixer": "^10.4.20",
     "chrome-launcher": "^1.2.1",
     "eslint": "^8.57.1",
-    "eslint-config-next": "^0.2.4",
+    "eslint-config-next": "^14.2.21",
     "eslint-plugin-react": "^7.37.5",
     "eslint-plugin-react-hooks": "^7.0.1",
     "husky": "^9.1.7",
@@ -83,7 +85,8 @@
     "k6": "^0.0.0",
     "lighthouse": "^13.0.3",
     "lint-staged": "^16.4.0",
-    "tailwindcss": "^4",
+    "postcss": "^8.4.49",
+    "tailwindcss": "^3.4.17",
     "ts-jest": "^29.4.6",
     "tsx": "^4.21.0",
     "typescript": "^5"