Replaces `community.docker.docker_image` with the modern
`docker_image_pull` module. Drops the `ansible_version` compatibility
ladder and the now-redundant `_container_image_force_pull` variable
(the new pull module handles registry refresh natively via `pull: always`).

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5191.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Roles affected: appservice-discord, appservice-irc, beeper-linkedin,
heisenbridge, hookshot, mautrix-bluesky, mautrix-discord,
mautrix-gmessages, mautrix-googlechat, mautrix-signal, mautrix-slack,
mautrix-twitter, mautrix-whatsapp, mautrix-wsproxy, mx-puppet-groupme,
mx-puppet-steam, postmoogle, sms, steam, cactus-comments, element,
fluffychat, schildichat, conduit, corporal, dendrite,
ldap-registration-proxy, media-repo, pantalaimon,
prometheus-nginxlog-exporter, registration, sygnal, synapse-admin,
user-verification-service.

For each role: renamed _docker_image* variables to _container_image*
(and _docker_src_files_path to _container_src_files_path where
applicable), added deprecation entries in validate_config.yml, and
updated group_vars/docs references.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

For each of the 34 roles (3 clients, 9 bots, 22 bridges), this commit:
- Adds `_restart_necessary: false` default variable
- Adds `register:` directives to config/image/systemd tasks
- Computes `_restart_necessary` via set_fact (OR of all .changed results)
- Wires `(_restart_necessary | bool)` in group_vars/matrix_servers

This allows the systemd service manager to skip unnecessary restarts
when running install-* tags and nothing actually changed.

Service roles and complex multi-service roles will follow separately.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

This:

- brings consistency - no more mixing `_name_prefix` and `_registry_prefix`
- adds extensibility - a future patch will allow reconfiguring all registry prefixes for all roles in the playbook

We still have `_docker_` vs `_container_` inconsistencies.
These may be worked on later.

This is done for a few reasons:

- less globals and more indepdendence for each role is better. We rely
  on various externally-hosted roles and they don't rely on this global
  either.

- `matrix_container_global_registry_prefix` could make people think they
  could just override this variable and have all their images pull from
  elsewhere. This is rarely the case, unless you've taken special care
  to mirror all the various components (from their respective
  registries) to your own. In such a case, you probably know what you're
  mirroring and can adjust individual variables.

- nowadays, various components live on different registries.
  With Docker Inc tightening rate limits for Docker Hub, it's even more
  likely that we'll see increased diversity in where images are hosted

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3518
- https://github.com/hifi/heisenbridge/issues/294

With this patch, when `matrix_heisenbridge_path_prefix` is the default
one we use (`/heisenbrdige`), URLs like this are constructed:

https://matrix.DOMAIN/heisenbridge/_heisenbridge/media/SERVER_NAME/MEDIA_ID/CHECKSUM/FILENAME

If `matrix_heisenbridge_path_prefix` is set to `/`, URLs like this are constructed:

https://matrix.DOMAIN/_heisenbridge/media/SERVER_NAME/MEDIA_ID/CHECKSUM/FILENAME

Our Traefik labels support handling both cases correctly.

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3470
- https://github.com/hifi/heisenbridge/releases/tag/v1.15.0

During testing, it appears that Heisenbridge generated media URLs
that look like this: `{media_url}/_matrix/media/v3/download/DOMAIN/FILE_ID/FILE_NAME`.

This seems off. We were expecting `{media_url}/_heisenbridge/media/something`
(e.g. `https://matrix.DOMAIN/heisenbridge/_heisenbridge/media/something`, leading to its own media proxy),
but Heisenbridge still seems to be generating URLs destined for the homeserver's Media API.

Until we figure out why that is, `media_url` remains pointed to the homeserver URL (just like before),
so that the bot can continue operating like before.

Related to 0241c71a4c

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3270#issuecomment-2143782962

With this change, it should be possible for people to adjust the Docker
dependency from `docker.service` to something else (e.g. `pkg-ContainerManager-dockerd.service`),
or to completely eliminate it by setting `devture_systemd_docker_base_docker_service_name` to an empty string.

This makes it easier for people to use the playbook against a Synology DSM server.

Without explicitly passing the `media_url` configuration,
Heisenbridge would try to guess it. It works most of the time,
but some people are experiencing trouble with it.

There's no need for wasteful work and for potential unreliability,
so we now configure the `media_url` explicitly.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2932

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.