Customize Client Agent scheme, host and port

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**Is your feature request related to a problem? Please describe.**
Currently trying to build a Remotely server that is running on Docker and Nginx reverse proxy. Running Remotely with https on another port that is not 443. Because either I cannot find the right http headers to send or remotely is not detecting the headers correctly, the clients can't connect because it defaults to port 443.

**Describe the solution you'd like**
Would like to run my server on HTTPS and custom port that is not 443. The fix from Issue 584 got me halfway there. However, it would be easier if the Server Config just let us define the exact server scheme, hostname, and port used to generate the EXE. I would not need to tinker with the proxy headers, which I cannot seem to get working.

**Describe alternatives you've considered**
Changing the server url on the client manually for the port.

**Additional context**
Add any other context or screenshots about the feature request here.

Start by locating the Server Config handling and the code that generates the client EXE, then trace how the server URL is built. The work is done when scheme, hostname, and port can be configured explicitly and generated clients use those values for connections; verify behavior with the relevant existing tests or build checks.

Written by the indexing model from the issue text.