fix: resolve DOMPurify XSS vulnerabilities (GHSA-v8jm-5vwx-cfxm, GHSA-v2wj-7wpq-c8vv)

Add yarn resolution to pin dompurify>=3.3.2, fixing transitive dependency
from swagger-ui-react that was stuck at 3.2.6.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -94,6 +94,9 @@
     "*.{js,jsx,ts,tsx}": "npm run lint:fix",
     "*.{js,jsx,ts,tsx,json,css,md,mdx}": "npm run prettier:fix"
   },
+  "resolutions": {
+    "dompurify": "^3.3.2"
+  },
   "keywords": [],
   "author": "",
   "license": "Apache-2.0"