Add managed service lifecycle support

[david-kariuki]

Summary

Add a shared framework for managing system services required by workstation modules without embedding direct systemctl commands throughout module implementations.

Service operations should be explicit, idempotent, dry-run aware, and integrated with execution planning and verification.

Scope

• Provide shared service-management utilities
• Detect whether the target system uses systemd before attempting systemd operations
• Support checking whether a service exists
• Support checking whether a service is enabled
• Support checking whether a service is active
• Support enabling and disabling services where explicitly requested
• Support starting, stopping, and restarting services where required
• Avoid restarting services when no relevant change occurred
• Route privileged service operations through the shared execution layer
• Integrate service actions with execution planning
• Support dry-run behaviour for all service operations
• Allow modules to declare required service state without calling systemctl directly
• Provide post-action verification of required service state
• Report unavailable or failed services clearly

Acceptance Criteria

• Modules do not need to execute systemctl directly
• Service existence and current state can be queried safely
• Already-satisfied service states are skipped
• Services are not restarted unnecessarily
• Privileged service operations use the shared execution layer
• Dry-run reports intended service changes without modifying the system
• Service actions appear in the execution plan
• Required service states can be verified after execution
• Missing required services fail with clear errors
• Systems without systemd fail or skip according to explicit module requirements
• Service-management behaviour can be tested without changing the developer workstation