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>

These variables track whether a database migration necessitates a service
restart. The new name avoids confusion with the conditional restart
feature introduced in af193043/9accc848/4a8df138, where
devture_systemd_service_manager handles restarting services whose
configuration or image changed. The old _requires_restart name was
ambiguous — it could be mistaken for the systemd_service_manager
mechanism — so _migration_requires_restart makes the purpose explicit.

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

Most `when` dict keys already were done correctly, but these few weren't.

ansible-core 2.19.0 reported the following errors for them:

> [WARNING]: Deprecation warnings can be disabled by setting `deprecation_warnings=False` in ansible.cfg.
> [DEPRECATION WARNING]: The `bool` filter coerced invalid value 'variable_name' (str) to False. This feature will be removed from ansible-core version 2.23.

Refer fd39392ec5 as well

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

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3698

* Rename variables matrix_bot_postmoogle_* with matrix_postmoogle_*

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

* Rename file names and references to those files

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

* Move variables block for /matrix-bridge-postmoogle

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

* Rename matrix_playbook_bot_postmoogle_ to matrix_playbook_bridge_postmoogle_

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

* Add matrix_playbook_migration_matrix_postmoogle_migration_validation_enabled

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

* Replace an install tag example with "-bot" prefix

The previous example seems to have been selected to show how components whose name contains "-bot-" needed to be specified.

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

---------

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