Add internal port support

[AWFX]

Hello. It is assumed that the container has a bridge type network interface. Its default internal port is 51820. If you use port forwarding, then everything works. Since this is a VPN, I would like to avoid network delays associated with the network adapter, so the host type is used as the network adapter. In this case, the wg0.conf configuration will have port 51820, not the one that was set via the SERVERPORT variable. My changes suggest using another environment variable that will help redefine the internal wireguard port.

P.S. This is my first PR, please don’t judge too harshly if possible.

[github-actions]

Thanks for opening this pull request! Be sure to follow the pull request template!

[LinuxServer-CI]

I am a bot, here is the pushed image/manifest for this PR:

ghcr.io/linuxserver/lspipepr-wireguard:1.0.20250521-r1-pkg-291ebaef-dev-b5c063d7fc97896ad39b951d8375462c9a3c54e4-pr-410

[j0nnymoe]

We've had a couple requests for this and I suspect that their stance on this hasn't changed.

I'm curious to know though what delays you think get added with bridge Vs host?

Also, you can just manually edit this yourself within the template of the container, this PR would break existing installs.

[AWFX]

The docker documentation says the following -

Host mode networking can be useful for the following use cases:
- To optimize performance

The docker bridge network uses a virtual switch, I suggest that in theory the performance may be lower (most likely not by much)

[aptalca]

1. We do not support host networking with this container
2. You can edit the server conf template as you wish

The docker bridge network uses a virtual switch, I suggest that in theory the performance may be lower (most likely not by much)

That's just a theory. I do not observe a real world difference as it easily saturates my gigabit connection.

[AWFX]

Well, I get it.