swarm-authelia: run the secret publisher and a journal forwarder inside the container

swarm-secret-publish and its path unit now run inside authelia's container,
beside the mint, and read each client secret at the path authelia writes it.
The host unit and host path unit, which read the secrets through the
container's root on the host, are gone, and so is
deploy.authelia.hostClientSecretDir, which only they read. The publisher keeps
its store identity, the secret-publisher leaf. The host hands the leaf and the
store's CA into the container as nspawn system credentials, and the unit loads
them; where this host mints the leaf, the container waits for swarm-bao-pki.
Authelia does not wait for the publisher, which retries every 30 seconds while
the store is down.

The container also runs the journal forwarder the other service containers
run, pushing to a receiver of its own on the swarm collector (serviceProducers
swarm-authelia) as a new machine OIDC client (swarm.authelia.otel.clientId)
that authelia registers for itself and the publisher carries to the store. The
fetch unit reads it back under the publisher's leaf, also handed to it as a
system credential, so the swarm-secret-publisher policy gains read on that one
leaf; its stanza keeps create and update, which the exact path would otherwise
take from the services/* prefix. Without the leaf the forwarder is off.

The container drops --link-journal=host, and the host collector stops reading
it. The services' "nothing at <path>" errors name the publisher in authelia's
container.

docs/swarm/sso.md

@@ -122,7 +122,7 @@ mechanism with flags.
 ### 1. All-local — one host runs both
 
 Nothing to configure at all. authelia mints each client's secret at its
-first boot, and `swarm-secret-publish` on its host writes it to the swarm
+first boot, and `swarm-secret-publish` in its container writes it to the swarm
 secret store at `swarm/services/<client id>/oidc/client`. A host-side unit
 then reads it from the store and writes it into the service's container:
 `swarm-bao-forge-oidc` for the forge, under the forge publisher's store