Replaced all hardcoded service name concatenations with the new get_service_name filter.
This ensures consistency, proper lowercase formatting, and correct handling of '@' suffixed units.
Added unittests for the filter (normal, custom suffix, '@'-units, and lowercase normalization).
Context: see ChatGPT discussion https://chatgpt.com/share/68a38beb-b9bc-800f-b7ed-cdd2b64b2604
This commit restructures systemctl service definitions and category mappings.
Motivation: Alarm-related bugs revealed inconsistencies in service and role handling.
Preparation step: lays the groundwork for fixing the alarm issues by aligning categories, roles, and service templates.
