update tailwind to v4

frontend/package.json

@@ -22,17 +22,17 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.2",
+    "@tailwindcss/postcss": "^4.1.18",
     "@types/react": "^19.2.7",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^5.1.2",
-    "autoprefixer": "^10.4.23",
     "eslint": "^9.39.2",
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.4.26",
     "globals": "^16.5.0",
     "postcss": "^8.5.6",
     "prettier": "^3.7.4",
-    "tailwindcss": "^3.4.19",
+    "tailwindcss": "^4.1.18",
     "typescript": "^5.9.3",
     "typescript-eslint": "^8.50.1",
     "vite": "^7.3.0"