Use backup_pvc for custom backup PVC name in templates
When backup_pvc is specified with create_backup_pvc: true, the PVC
template and ownerReference removal used the hardcoded default name
(deployment_name-backup-claim) instead of the user-specified name.
This caused the management pod to reference a PVC that didn't exist.
Replace backup_claim variable with backup_pvc throughout the backup
role so the resolved PVC name is used consistently in all templates.
Authored By: Adam Knochowski <aknochow@redhat.com>
Assisted By: Claude