fix(deps): update nextra monorepo to v4

Author: renovate[bot]

docs/package.json

@@ -15,8 +15,8 @@
   },
   "dependencies": {
     "next": "15.1.6",
-    "nextra": "3.3.1",
-    "nextra-theme-docs": "3.3.1",
+    "nextra": "4.1.0",
+    "nextra-theme-docs": "4.1.0",
     "react": "19.0.0",
     "react-dom": "19.0.0"
   },