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/srv-web-7-4-core/templates/nginx.conf.j2

@@ -36,8 +36,6 @@ http
                   '"X-Forwarded-For: $http_x_forwarded_for" '
                   '"Scheme: $scheme" "Protocol: $server_protocol" "ServerName: $server_name"';
   access_log  /dev/stdout  debug;
-{% else %}
-  access_log  /dev/stdout  debug;
 {% endif %}
   error_log  /dev/stderr  info;