build(docs): upgrade nextra to v3 and update config

docs/package.json

@@ -9,9 +9,12 @@
     "@vercel/analytics": "^1.1.1",
     "docsgpt-react": "^0.5.1",
     "next": "^15.5.9",
-    "nextra": "^2.13.2",
-    "nextra-theme-docs": "^2.13.2",
+    "nextra": "^3.3.1",
+    "nextra-theme-docs": "^3.3.1",
     "react": "^18.2.0",
     "react-dom": "^18.2.0"
+  },
+  "devDependencies": {
+    "typescript": "^5.9.3"
   }
 }