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/web-app-discourse/tasks/02_reset.yml

@@ -16,6 +16,7 @@
       - docker_compose is defined
       - ports is defined
     fail_msg: "Load roles/docker-compose/vars/docker-compose.yml and set `database_type` first."
+  when: MODE_ASSERT | bool
 
 - name: "Disconnect DB container from Discourse networks"
   ansible.builtin.command: