🛡️ Sentinel: [HIGH] Mitigate XSS in CodeBlock rendering via DOMPurify

Sanitize HTML string generated by Shiki before rendering it via `dangerouslySetInnerHTML` in CodeBlockEmbeddable and CodeBlockSidebar.

package.json

@@ -20,6 +20,7 @@
   "dependencies": {
     "@excalidraw/excalidraw": "^0.18.1",
     "@modelcontextprotocol/sdk": "^1.29.0",
+    "dompurify": "^3.4.8",
     "fast-json-patch": "^3.1.1",
     "mcp-handler": "^1.1.0",
     "react": "^19.2.6",
@@ -29,6 +30,7 @@
   },
   "devDependencies": {
     "@types/bun": "^1.3.14",
+    "@types/dompurify": "^3.2.0",
     "@types/react": "^19.2.15",
     "@types/react-dom": "^19.2.3",
     "prettier": "^3.8.3",