[optimizer-docker] Support UNIX domain sockets

Please allow for the optimizer-docker web server to listen on a configurable UNIX domain socket. Given that the service is almost always bound to be used locally it seems to be a feature that would be useful to many.

The issue names the optimizer-docker web server but no file or test. Start by locating its server entry point and current listener configuration, then verify that a configurable UNIX domain socket supports local connections while existing network binding remains intact.

Written by the indexing model from the issue text.