infra(sys-service): centralize async control + pre-deploy backup safeguard

- Added MODE_BACKUP to trigger backup before the rest of the deployment

- sys-ctl-bkp-docker-2-loc: force linear sync and force flush when MODE_BACKUP is true

- Unified name resolution via system_service_name across handlers and tasks

- Introduced system_service_force_linear_sync and system_service_force_flush (rename from system_force_flush)

- Drive async/poll via system_service_async/system_service_poll using omit when disabled

- Propagated per-role overrides (cleanup, repair, cert tasks) for clarity and safety

- Minor formatting and consistency cleanups

Why: Ensure the backup runs before the deployment routine to safeguard data integrity.

Refs: Conversation https://chatgpt.com/share/68de4c41-b6e4-800f-85cd-ce6949097b5e
Signed-off-by: Kevin Veen-Birkenbach <kevin@veen.world>

roles/sys-service/tasks/05_service.yml

@@ -31,7 +31,7 @@
 - name: "setup systemctl '{{ system_service_id }}'"
   template:
     src:  "{{ system_service_template_src }}"
-    dest: "{{ [ PATH_SYSTEM_SERVICE_DIR, system_service_id | get_service_name(SOFTWARE_NAME) ] | path_join }}"
+    dest: "{{ [ PATH_SYSTEM_SERVICE_DIR, system_service_name ] | path_join }}"
     owner: root
     group: root
     mode: '0644'
@@ -46,5 +46,5 @@
     command: /bin/true
     notify: refresh systemctl service
     when: not system_service_uses_at
-  when: system_force_flush | bool
+  when: system_service_force_flush | bool