Update cart badge on ticket purchase via OOB swap

The buy_tickets response now includes an OOB swap of #cart-mini
so the cart badge count updates immediately when tickets are reserved.

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

templates/_types/tickets/_buy_result.html

@@ -1,4 +1,8 @@
 {# Shown after ticket purchase — replaces the buy form #}
+{# OOB: refresh cart badge to reflect new ticket count #}
+{% from '_types/cart/_mini.html' import mini %}
+{{ mini(oob='true') }}
+
 <div id="ticket-buy-{{ entry.id }}" class="rounded-xl border border-emerald-200 bg-emerald-50 p-4">
   <div class="flex items-center gap-2 mb-3">
     <i class="fa fa-check-circle text-emerald-600" aria-hidden="true"></i>