Replace misleading system total quotas with actual service-specific
quota detection. Services now only show quotas when real limits exist.
Changes:
- Add get_service_disk_quota method with filesystem quota detection
- Add check_filesystem_quota and docker storage quota helpers
- Remove automatic assignment of system totals as fake quotas
- Update dashboard formatting to show usage only when no quota exists
Display behavior:
- Services with real limits: "2.1/8.0" (usage/quota)
- Services without limits: "2.1" (usage only)
This provides accurate monitoring instead of misleading system capacity
values that suggested all services had massive quotas.