Fix FRR old namespace cleanup error handling in reconcileDelete

Return the error instead of just logging it when cleanup of
FRRConfigurations from the old namespace fails during CR deletion.
Without this, the finalizer is removed and the CR is garbage collected
even if old-namespace FRRConfigurations were not successfully deleted,
potentially leaving orphaned resources.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lmiccini

internal/controller/network/bgpconfiguration_controller.go

@@ -384,7 +384,7 @@ func (r *BGPConfigurationReconciler) reconcileDelete(ctx context.Context, instan
 
 	if frrNamespace != instance.Spec.FRRConfigurationNamespace {
 		if err := r.cleanupOldNamespaceFRRConfigurations(ctx, instance, instance.Spec.FRRConfigurationNamespace); err != nil {
-			Log.Error(err, "Failed to cleanup FRRConfigurations from old namespace", "namespace", instance.Spec.FRRConfigurationNamespace)
+			return ctrl.Result{}, fmt.Errorf("error cleaning up FRRConfigurations from old namespace %s: %w", instance.Spec.FRRConfigurationNamespace, err)
 		}
 	}