Every hive with hyperhive enabled ran its own hive-forge container, and
its gateway answered forge.<swarm> with its own bridge IP, so on a
multi-host swarm each hive talked to its own forge.
deploy.forgejo.enable defaults to false and allSwarmServices sets it with
mkDefault, like authelia and bao; singleHostSwarm gets it through that.
The forge's OIDC client moves to a glue module gated on authelia, so a
split authelia/forge swarm still registers it. CI now requires the forge
on the same host, and the controller's forgeTokenFile defaults to null
where the forge is not.
Closes#4705
Refs #3782
