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-discord/defaults/main.yml

@@ -245,3 +245,13 @@ matrix_mautrix_discord_bridge_encryption_key_sharing_allow: "{{ matrix_mautrix_d
 # On Conduit versions before 0.5.0 this option prevented users from joining spaces created by the bridge.
 # Setting this to false fixed the issue.
 matrix_mautrix_discord_bridge_restricted_rooms: true
+
+# matrix_mautrix_discord_restart_necessary controls whether the service
+# will be restarted (when true) or merely started (when false) by the
+# systemd service manager role (when conditional restart is enabled).
+#
+# This value is automatically computed during installation based on whether
+# any configuration files, the systemd service file, or the container image changed.
+# The default of `false` means "no restart needed" — appropriate when the role's
+# installation tasks haven't run (e.g., due to --tags skipping them).
+matrix_mautrix_discord_restart_necessary: false

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

@@ -56,10 +56,10 @@
     force_source: "{{ matrix_mautrix_discord_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_discord_docker_image_force_pull }}"
   when: not matrix_mautrix_discord_container_image_self_build
-  register: result
+  register: matrix_mautrix_discord_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_discord_container_image_pull_result is not failed
 
 - name: Ensure Mautrix discord repository is present on self-build
   ansible.builtin.git:
@@ -91,6 +91,7 @@
     mode: 0644
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_mautrix_discord_config_result
 
 - name: Ensure mautrix-discord registration.yaml installed
   ansible.builtin.copy:
@@ -99,6 +100,7 @@
     mode: 0644
     owner: "{{ matrix_user_name }}"
     group: "{{ matrix_group_name }}"
+  register: matrix_mautrix_discord_registration_result
 
 - name: Ensure mautrix-discord support files installed
   ansible.builtin.template:
@@ -109,6 +111,7 @@
     group: "{{ matrix_group_name }}"
   with_items:
     - labels
+  register: matrix_mautrix_discord_support_files_result
 
 - name: Ensure mautrix-discord container network is created
   community.general.docker_network:
@@ -124,6 +127,18 @@
     mode: 0644
   register: matrix_mautrix_discord_systemd_service_result
 
+- name: Determine whether matrix-mautrix-discord needs a restart
+  ansible.builtin.set_fact:
+    matrix_mautrix_discord_restart_necessary: >-
+      {{
+        matrix_mautrix_discord_migration_requires_restart | default(false)
+        or matrix_mautrix_discord_config_result.changed | default(false)
+        or matrix_mautrix_discord_registration_result.changed | default(false)
+        or matrix_mautrix_discord_support_files_result.changed | default(false)
+        or matrix_mautrix_discord_systemd_service_result.changed | default(false)
+        or matrix_mautrix_discord_container_image_pull_result.changed | default(false)
+      }}
+
 - name: Ensure matrix-mautrix-discord.service restarted, if necessary
   ansible.builtin.service:
     name: "matrix-mautrix-discord.service"