feat: install react-helmet-async and gray-matter, add HelmetProvider

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -20,12 +20,14 @@
     "@types/spark-md5": "^3.0.5",
     "browser-image-compression": "^2.0.2",
     "clsx": "^2.1.1",
+    "gray-matter": "^4.0.3",
     "html-to-image": "^1.11.13",
     "katex": "^0.16.27",
     "lucide-react": "^0.344.0",
     "mathml2omml": "^0.5.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "react-helmet-async": "^3.0.0",
     "react-hot-toast": "^2.6.0",
     "react-markdown": "^10.1.0",
     "react-router-dom": "^7.13.1",