feat: implement security audit fixes SEC-001 through SEC-031

client/package.json

@@ -31,6 +31,7 @@
     "@vueuse/core": "^14.2.1",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "dompurify": "^3.3.3",
     "echarts": "^6.0.0",
     "howler": "^2.2.4",
     "lucide-vue-next": "^1.0.0",
@@ -49,6 +50,7 @@
   },
   "devDependencies": {
     "@tsconfig/node24": "^24.0.4",
+    "@types/dompurify": "^3.2.0",
     "@types/jsdom": "^28.0.1",
     "@types/node": "^25.6.0",
     "@vitejs/plugin-vue": "^6.0.5",