* 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>

These three roles have multiple variable prefixes each:
- kakaotalk: matrix_appservice_kakaotalk + matrix_appservice_kakaotalk_node
- telegram: matrix_mautrix_telegram + matrix_mautrix_telegram_lottieconverter
- synapse: matrix_synapse + matrix_synapse_customized + matrix_synapse_rust_synapse_compress_state

For each: renamed _docker_image* to _container_image* (and _docker_src*,
_docker_repo* where applicable), added deprecation entries in
validate_config.yml, updated group_vars references, and moved
deprecation tasks to the front of validate_config.yml.

Co-Authored-By: Claude Opus 4.6 <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.

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.

Adds support for: https://src.miscworks.net/fair/matrix-appservice-kakaotalk

This is pretty similar to
https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1977
which just appeared, but has mostly been done independently.

I've taken some inspiration and did some fixups based on that PR.
Thanks to https://github.com/hnarjis for taking the time to contribute!

Notable differences between this branch compared to that PR:

- better naming and documentation around the "configuration" variables
- no unnecessary (5 sec.) intentional delay when starting `matrix-appservice-kakaotalk-node.service`
- stores configuration in `config/`, not in `data/`
- passes configuration as read-only and starts the bridge with (`--no-update`) to ensure no changes are made to it
- starts containers more securely - with `matrix:matrix` user:group (not `root`) and
  reduced capabilities (`--cap-drop=ALL`)
- uses `tcp` for communication between the "node" and the appservice (simpler than sharing unix sockets)
- `registration.yaml` which is closer to the one generated by `matrix-appservice-kakaotalk` (no `de.sorunome.msc2409.push_ephemeral` stuff, etc.)
- `registration.yaml` which is more customizable (customizable bot username and prefix for puppets - see `matrix_appservice_kakaotalk_appservice_bot_username` and `matrix_appservice_kakaotalk_user_prefix`)
- less fragile and more extensible bridge permissions configuration via `matrix_appservice_kakaotalk_bridge_permissions`. Doing `{% if matrix_admin %}` in the bridge configuration sometimes causes syntax problems (I hit some myself) and is not ideal. Other bridges should be redone as well.
- configurable command prefix for the bridge, instead of hardcoding `!kt` (see `matrix_appservice_kakaotalk_command_prefix`)
- logging that is more consistent with the rest of the playbook (console / journald only, no logging to files), as well as configurable log level (via `matrix_appservice_kakaotalk_logging_level`)
- somewhat more detailed documentation (`docs/configuring-playbook-bridge-appservice-kakaotalk.md`)
- removed some dead code (data relocation tasks from `tasks/setup_install.yml`, as well as likely unnecessary SQLite -> Postgres migration)