feat: implement hx-boost for reliable loading indication

templates/booking/create/authenticate.html.twig

@@ -39,7 +39,7 @@
                 {% endif %}
 
                 <div class="pb-4">
-                    <form action="{{ path('app_login') }}" method="post" {{ stimulus_action('loading', 'show') }}>
+                    <form action="{{ path('app_login') }}" method="post">
                         <div class="mb-4">
                             <label for="username" class="mb-1 font-semibold text-white">
                                 E-Mail: