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>

assets/css/ticket.css

@@ -365,3 +365,7 @@ kbd {
 
 /* Metadata selects use .lt-display-field (base.css) in read mode
    instead of disabled — full opacity, non-interactive, no fading. */
+
+
+/* Skeleton placeholder for comment lazy-load */
+.comment-skeleton { margin-bottom: 0.75rem; }