* feat: support container_network=host across all roles + systemd templates

Mirror the pattern Slavi introduced for matrix-coturn (aafa8f0) across the
fork: every 'Ensure X container network is created' task gets a
'when: <var> not in ["", "host"]' guard so MDAD does not try to
docker_network create a network literally named 'host' (returns 403,
since host is a pre-defined Docker network).

Mirror the same guard in every systemd unit template that does
'ExecStartPre=docker network connect <addnet> <container>' loops over
matrix_<role>_container_additional_networks: skip the connects when the
container is on host networking (where additional --network attaches
are invalid).

Unblocks DiD setups where MDAD-managed containers share their host's
network namespace (matrix-mdad outer compose service joined to central
postgres/openldap networks) to reach external services on the outer
Docker daemon.

* Simplify container network guards (!= 'host') and fix duplicate when

Guarding on the empty string ('') as well was misleading: systemd unit
templates still render an unconditional --network= flag, so an empty
network value produces a broken docker create command. Only 'host' is
actually supported, so only guard on that. This also matches the
existing convention in the Traefik role
(when: traefik_container_network != 'host').

Also fix a duplicate when key in the meshtastic-relay role, where the
network-creation task already had a when condition - the two are now
combined into a list.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4445

`-t` works on both old and new Docker versions, so it's best to use that.

* add synapse-auto-compressor workaround, fixes #3397

* Clarify what the PG-prefixed variables are for

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

This provides an additional security benefit. The password won't leak in
the process list anymore.

It will, additionally, be connected to the devture-postgres network, if
devture-postgres is enabled.

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.

People often report and ask about these "failures".
More-so previously, when the `docker kill/rm` output was collected,
but it still happens now when people do `systemctl status
matrix-something` and notice that it says "FAILURE".

Suppressing to avoid further time being wasted on saying "this is
expected".

Reverts b1b4ba501fdfaa, 90c9801c560b6, a3c84f78ca9c65a, ..

I haven't really traced it (yet), but on some servers, I'm observing
`ansible-playbook ... --tags=start` completing very slowly, waiting
to stop services. I can't reproduce this on all Matrix servers I manage.
I suspect that either the systemd version is to blame or that some
specific service is not responding well to some `docker kill/rm` command.

`ExecStop` seems to work great in all cases and it's what we've been
using for a very long time, so I'm reverting to that.