chore: Update frontend devDependencies to latest

- @types/react: 19.1.0 -> 19.2.14
- @types/react-dom: 19.1.1 -> 19.2.3
- postcss: 8.4.50 -> 8.5.6

Note: @types/node kept at 22.x for Node 20 compatibility

frontend/package.json

@@ -26,11 +26,11 @@
   },
   "devDependencies": {
     "@types/node": "^22.12.0",
-    "@types/react": "^19.1.0",
-    "@types/react-dom": "^19.1.1",
+    "@types/react": "^19.2.14",
+    "@types/react-dom": "^19.2.3",
     "typescript": "^5.9.3",
     "tailwindcss": "^3.4.19",
-    "postcss": "^8.4.50",
+    "postcss": "^8.5.6",
     "autoprefixer": "^10.4.24"
   }
 }