Read-only enrichment plugin, not an import/discovery plugin. For each
configured Docker host (via Docker Socket Proxy, never /var/run/docker.sock
directly), lists that host's containers under the host device's own
Device Details -> Plugins -> DOCKERDISC tab.
- Never creates a device, for either a host or a container - matches
against hosts already discovered the normal way (ARP/Nmap).
- Every container is listed (bridge/overlay included), not only
macvlan/ipvlan ones - a container only gets its own MAC/IP shown when
it has a macvlan/ipvlan network.
- Host MAC auto-detected via the Socket Proxy's /info -> Devices.devName
match, with a manual fallback.