security improvements

frontend/package.json

@@ -16,6 +16,7 @@
   },
   "dependencies": {
     "@xyflow/react": "^12.0.0",
+    "dompurify": "^3.3.3",
     "html-to-image": "^1.11.13",
     "marked": "^17.0.5",
     "react": "^18.3.0",
@@ -24,6 +25,7 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",
+    "@types/dompurify": "^3.0.5",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@types/three": "^0.183.1",