Make Ports dynamic

Hello,
I want to run multiple servers with this webrcon interface and so I need to change the ports which is no problem but the webinterface expects the Backend to still listen at Port 4327 so it can not connect to the websocket at 4327. Maybe you can make this dynamic so I can specify the new Port with an env-variable

Start by locating where the web interface assumes the backend websocket listens on port 4327 and review how the Docker image exposes configuration through environment variables. Done means a configurable port can be supplied through an environment variable and multiple server instances can connect to their respective websocket ports.

Written by the indexing model from the issue text.