- Replace complex multi-strategy detection with single deterministic method
- Remove estimate_service_disk_usage and all fallback strategies
- Use simple get_service_disk_usage method with clear logic:
* Defined path exists → use only that path
* Defined path fails → return None (shows as '-')
* No defined path → use systemctl WorkingDirectory
* No estimates or guessing ever
Fixes misleading 5MB estimates when defined paths fail due to permissions.