fix(deps): update nextra monorepo to v4

Author: renovate[bot]

package.json

@@ -24,8 +24,8 @@
     "eslint-config-next": "^15.1.0",
     "eslint-config-prettier": "^10.0.0",
     "next": "^14.2.4",
-    "nextra": "^3.0.0",
-    "nextra-theme-docs": "^3.0.0",
+    "nextra": "^4.0.0",
+    "nextra-theme-docs": "^4.0.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "react-icons": "^5.2.1",