fix: show warning flashes in the admin layout

templates/_partials/_flashes_admin.html.twig

@@ -7,3 +7,6 @@
 {% if app.session.flashBag.peek('info')|length > 0 %}
     {% include '_partials/_toast.html.twig' with { level: 'info', messages: app.flashes('info') } %}
 {% endif %}
+{% if app.session.flashBag.peek('warning')|length > 0 %}
+    {% include '_partials/_toast.html.twig' with { level: 'warning', messages: app.flashes('warning') } %}
+{% endif %}