Implement disk quota/total display in services widget showing usage/quota
format. When services don't have specific disk quotas configured, use
system total disk capacity as the quota value.
Changes:
- Add disk_quota_gb field to ServiceData struct in agent
- Add disk_quota_gb field to ServiceInfo struct in dashboard
- Update format_disk_value to show usage/quota format
- Use system disk total capacity as default quota for services
- Rename DiskUsage.total_gb to total_capacity_gb for clarity
Services will now display disk usage as "5.2/500.0 GB" format where
500.0 GB is either the service's specific quota or system total capacity.
Christoffer Martinsson
630d2ff674