Fresh Docker installs without ADMIN_PASSWORD generated two different random
passwords: Go wrote /opt/rustdesk/.admin_credentials while the panel
authenticated against auth.db seeded by Node.js. Pre-bootstrap a shared
password in entrypoints before supervisord / server start.
Refs #385
Thanks: INSOLVE (Honorary); Marco Jakobs (@jacotec); MyNameisStitch (@MyNameisStitch); Redspin (@playerumpknow)