Rename _requires_restart to _migration_requires_restart across all custom roles

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>

roles/custom/matrix-registration/tasks/setup_install.yml

@@ -11,7 +11,7 @@
 ---
 
 - ansible.builtin.set_fact:
-    matrix_registration_requires_restart: false
+    matrix_registration_migration_requires_restart: false
 
 - when: "matrix_registration_database_engine == 'postgres'"
   block:
@@ -40,7 +40,7 @@
               additional_psql_statements_db_name: "{{ matrix_registration_database_name }}"
 
         - ansible.builtin.set_fact:
-            matrix_registration_requires_restart: true
+            matrix_registration_migration_requires_restart: true
 
 - name: Ensure matrix-registration paths exist
   ansible.builtin.file:
@@ -135,4 +135,4 @@
     name: "matrix-registration.service"
     state: restarted
     daemon_reload: true
-  when: "matrix_registration_requires_restart | bool"
+  when: "matrix_registration_migration_requires_restart | bool"