[feature] Add support for non-default Nginx external ports

[c-gabri]

Is your feature request related to a problem? Please describe.
At present, the nginx container is hardcoded to listen on the default HTTPS/HTTP ports 443/80 of the host. This does not work, for example, on installations meant to run behind a reverse proxy on the same host, which is quite common for Docker applications.

Describe the solution you'd like
Users should be able to set custom Nginx HTTPS/HTTP external ports using .env variables.

Describe alternatives you've considered
If following the Docker Compose installation method, users could achieve the same result by setting the desired ports in docker-compose.yml after cloning the project, but this is less elegant, incongruent with how other options are set and incompatible with the auto-install script installation method.

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