Add comment skeleton loaders, workflow validation, monthly schedule fix

- TicketView.php: Show 3 lt-skeleton-card placeholders in the comment list
  while "Load more" fetches; skeletons are removed on resolve or error
- ticket.css: Add .comment-skeleton margin spacing
- WorkflowDesignerView.php + manage_workflows.php: Prevent creating/editing
  status transitions where from_status === to_status (client + server check)
- RecurringTicketsView.php: Expand monthly day picker from 28 to 31 days
  (days 29-31 labelled "last day in short months")
- RecurringTicketModel.php: Clamp monthly schedule day to last day of target
  month using format('t') instead of hard-capping at 28

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

views/admin/RecurringTicketsView.php

@@ -212,10 +212,10 @@ function updateScheduleOptions() {
         });
     } else if (type === 'monthly') {
         dayRow.classList.remove('is-hidden');
-        for (var i = 1; i <= 28; i++) {
+        for (var i = 1; i <= 31; i++) {
             var opt = document.createElement('option');
             opt.value = String(i);
-            opt.textContent = 'Day ' + i;
+            opt.textContent = 'Day ' + i + (i > 28 ? ' (last day in short months)' : '');
             daySelect.appendChild(opt);
         }
     }