Clarify PVC resize behavior for mounted vs unmounted volumes

Update the LVMS snapshot size fix procedure to accurately reflect that:
- Mounted PVCs (pods running): Resize happens automatically via CSI
  online resize, no pod restart required
- Unmounted PVCs (no pods): Resize is applied when PVC is next mounted,
  may need to trigger backup job manually

Tested with Glance PVCs (running pods) - confirmed automatic resize.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: stuggi

docs/dev/backup-restore-storage-volumes.md

@@ -430,10 +430,15 @@ oc edit pvc <pvc-name> -n openstack
 #       requests:
 #         storage: 5Gi
 
-# 2. Restart pods using the PVC to apply the resize
-# For Galera backup PVCs, restart the backup job or wait for next scheduled backup
-# For other service PVCs, restart the service pods:
-oc delete pod -n openstack -l service=<service-name>
+# 2. Wait for resize to complete
+# For PVCs with pods currently running (e.g., Glance, Cinder):
+#   - Resize happens automatically, no pod restart needed
+#   - Kubernetes and CSI driver handle online resize
+
+# For PVCs with NO pods running (e.g., Galera backup PVCs):
+#   - Resize is applied when the PVC is next mounted
+#   - Either wait for next backup job or trigger one manually:
+oc create job manual-backup --from=cronjob/<backup-cronjob-name> -n openstack
 
 # 3. Verify the PVC capacity was updated
 oc get pvc <pvc-name> -n openstack -o jsonpath='{.status.capacity.storage}'