fix(admin): guard htmx:confirm handler against empty question

The handler called evt.preventDefault() unconditionally, so auto-poll
requests (hx-trigger="every 5s", no hx-confirm) caused an empty dialog
to pop up every 5 seconds. Add an early return when evt.detail.question
is falsy so only actual hx-confirm interactions are intercepted.

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

web/src/padelnomics/admin/templates/admin/base_admin.html

@@ -247,6 +247,7 @@ function confirmAction(message, form) {
 
 // Intercept hx-confirm to use the styled dialog instead of window.confirm()
 document.body.addEventListener('htmx:confirm', function(evt) {
+  if (!evt.detail.question) return; // no hx-confirm on this element, let HTMX proceed
   var dialog = document.getElementById('confirm-dialog');
   if (!dialog) return; // fallback: let HTMX use native confirm
   evt.preventDefault();