feat: back-button in booking create flow

templates/booking/create/step_2_participant.html.twig

@@ -37,8 +37,8 @@
         <div class="shrink-0 bg-primary-dark px-4 lg:px-8 py-2 lg:py-4 z-20">
             <div class="flex justify-between">
                 <a href="{{ path('app_booking_create_step_2') }}"
-                   class="inline-flex items-center justify-center bg-gray-200 rounded-md w-10 h-10">
-                    <svg class="w-8 h-8" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><rect width="256" height="256" fill="none"/><line x1="200" y1="56" x2="56" y2="200" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/><line x1="200" y1="200" x2="56" y2="56" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="16"/></svg>
+                   class="button button--secondary">
+                    Zurück
                 </a>
                 <button type="submit" class="button button--primary" {{ qa_attribute('btn-submit') }}>
                     Speichern