Use nginx port for vite hmr if nginx is enabled

What does this merge request do and why?

This MR fixes a problem where the websocket connection to /vite-ruby can’t be established when using nginx.

How to set up and validate locally

1. Enable nginx: gdk config set nginx.enabled true
2. Enable vite gdk config set vite.enabled true && gdk config set webpack.enabled false
3. Run gdk reconfigure
4. Run gdk start
5. Open the local GitLab in your browser, see that it works

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.