Allow server to be configured via .env vars

[Valkyrien04]

current server environment variables should be the same as the hardcoded vars from before, but moving them onto env vars with defaults allows server operators to set the options as needed without those options being overwritten on a server update. This also makes them easier to change when using popular docker tools like portainer to run the server.

[jdhirst]

@Valkyrien04 Looks good to me, thanks for the contribution!