refactor: improve service handling and introduce MODE_ASSERT

- Improved get_service_name filter plugin (clearer suffix handling, consistent var names).
- Added MODE_ASSERT flag to optionally execute validation/assertion tasks.
- Fixed systemd unit handling: consistent use of %I instead of %i, correct escaping of instance names.
- Unified on_failure behavior and alarm composer scripts.
- Cleaned up redundant logging, handlers, and debug config.
- Strengthened sys-service template resolution with assert (only active when MODE_ASSERT).
- Simplified timer and suffix handling with get_service_name filter.
- Hardened sensitive tasks with no_log.
- Added conditional asserts across roles (Keycloak, DNS, Mailu, Discourse, etc.).

These changes improve consistency, safety, and validation across the automation stack.

Conversation: https://chatgpt.com/share/68a4ae28-483c-800f-b2f7-f64c7124c274

roles/sys-daemon/tasks/01_reset.yml

@@ -7,7 +7,9 @@
     that:
       - SYSTEMD_MANAGER_CONF_DIR | regex_search('^/etc/systemd/system\.conf\.d/?$')
     fail_msg: "SYSTEMD_MANAGER_CONF_DIR must be /etc/systemd/system.conf.d"
-  when: SYSTEMD_MANAGER_RESET_PURGE | bool
+  when:
+    - SYSTEMD_MANAGER_RESET_PURGE | bool
+    - MODE_ASSERT | bool
 
 - name: "Purge manager drop-in directory (remove)"
   file: