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

group_vars/all/08_timer.yml

@@ -2,7 +2,6 @@
 # Service Timers
 
 ## Meta
-SYS_TIMER_SUFFIX:       ".{{ SOFTWARE_NAME | lower }}.timer"
 SYS_TIMER_ALL_ENABLED:  "{{ not MODE_DEBUG }}"   # Runtime Variables for Process Control - Activates all timers, independend if the handlers had been triggered
 
 ## Server Tact Variables