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/handlers/main.yml

@@ -1,19 +1,19 @@
 - name: "Enable systemctl service"
   systemd:
-    name: "{{ system_service_id | get_service_name(SOFTWARE_NAME) }}"
+    name: "{{ system_service_name }}"
     enabled: yes
     daemon_reload: true
   become: true
-  async:  "{{ ASYNC_TIME if ASYNC_ENABLED | bool else omit }}"
-  poll:   "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"
+  async:  "{{ system_service_async }}"
+  poll:   "{{ system_service_poll }}"
   listen: refresh systemctl service
 
 - name: "Set systemctl service state"
   systemd:
-    name: "{{ system_service_id | get_service_name(SOFTWARE_NAME) }}"
+    name: "{{ system_service_name }}"
     state: "{{ system_service_state }}"
   become: true
-  async:  "{{ ASYNC_TIME if ASYNC_ENABLED | bool else omit }}"
-  poll:   "{{ ASYNC_POLL if ASYNC_ENABLED | bool else omit }}"
+  async:  "{{ system_service_async }}"
+  poll:   "{{ system_service_poll }}"
   when:   not (system_service_suppress_flush | bool)
   listen: refresh systemctl service