Fix admin order page blank redirect after status/note update

Missing ob_start() meant HTML was output before POST handler ran,
so header() redirects silently failed after saving changes.

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

admin/order.php

@@ -2,7 +2,7 @@
 /**
  * Tom's Java Jive - Admin Order Detail
  */
-
+ob_start();
 $pageTitle = 'Order Details';
 require_once __DIR__ . '/includes/header.php';