Add conditional restart support to client, bot, and bridge roles

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>

roles/custom/matrix-bridge-mautrix-slack/tasks/setup_install.yml

@@ -55,10 +55,10 @@
     force_source: "{{ matrix_mautrix_slack_docker_image_force_pull if ansible_version.major > 2 or ansible_version.minor >= 8 else omit }}"
     force: "{{ omit if ansible_version.major > 2 or ansible_version.minor >= 8 else matrix_mautrix_slack_docker_image_force_pull }}"
   when: not matrix_mautrix_slack_container_image_self_build
-  register: result
+  register: matrix_mautrix_slack_container_image_pull_result
   retries: "{{ devture_playbook_help_container_retries_count }}"
   delay: "{{ devture_playbook_help_container_retries_delay }}"
-  until: result is not failed
+  until: matrix_mautrix_slack_container_image_pull_result is not failed
 
 - name: Ensure Mautrix slack repository is present on self-build
   ansible.builtin.git:
@@ -90,6 +90,7 @@
     mode: 0644
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_mautrix_slack_config_result
 
 - name: Ensure mautrix-slack registration.yaml installed
   ansible.builtin.copy:
@@ -98,6 +99,7 @@
     mode: 0644
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_mautrix_slack_registration_result
 
 - name: Ensure matrix-mautrix-slack container network is created
   community.general.docker_network:
@@ -113,6 +115,17 @@
     mode: 0644
   register: matrix_mautrix_slack_systemd_service_result
 
+- name: Determine whether matrix-mautrix-slack needs a restart
+  ansible.builtin.set_fact:
+    matrix_mautrix_slack_restart_necessary: >-
+      {{
+        matrix_mautrix_slack_migration_requires_restart | default(false)
+        or matrix_mautrix_slack_config_result.changed | default(false)
+        or matrix_mautrix_slack_registration_result.changed | default(false)
+        or matrix_mautrix_slack_systemd_service_result.changed | default(false)
+        or matrix_mautrix_slack_container_image_pull_result.changed | default(false)
+      }}
+
 - name: Ensure matrix-mautrix-slack.service restarted, if necessary
   ansible.builtin.service:
     name: "matrix-mautrix-slack.service"