Wrong version in package.json

Sorry to disturb once again...

[frontend/package.json](https://github.com/NginxProxyManager/nginx-proxy-manager/blob/develop/frontend/package.json) is showing version 2.0.0 instead of 2.13.1.

This results in:

<img width="439" height="82" alt="Image" src="https://github.com/user-attachments/assets/1b07c0f0-f49c-4a3a-b3b4-cc7901458799" />

