fix alert colors

src/client/styles/scss/_override-bootstrap-variables.scss

@@ -59,6 +59,10 @@ $modal-content-border-width: 0;
 $modal-header-padding-y: 0.75rem;
 $modal-header-padding-x: 1rem;
 
+//== Alerts
+$alert-bg-level: -2;
+$alert-border-level: 0;
+
 //== Progress bar
 $progress-height: 4px;
 $progress-border-radius: $border-radius-sm;