fix: destination cards show a tour photo again

vc_term_image_url() cached empty results for 12h and relied on an SQL
meta comparison to find a tour with a photo; destination cards site-wide
(homepage and region pages) were blank. Read the photo in PHP from up to
10 tours (primary, else first gallery image), use a fresh cache key, and
expire empty results after an hour. Plugin 1.9.3.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

viator-collector/viator-collector.php

@@ -4,13 +4,13 @@ defined('ABSPATH') || exit;
 /**
  * Plugin Name: Viator Collector
  * Description: Import Viator tours using the Viator Partner API and display them with native WordPress post types, templates, and shortcodes.
- * Version: 1.9.2
+ * Version: 1.9.3
  * Author: Amir Bagheri
  * License: GPL-2.0-or-later
  * Text Domain: viator-collector
  */
 
-define('VC_VERSION', '1.9.2');
+define('VC_VERSION', '1.9.3');
 define('VC_PLUGIN_FILE', __FILE__);
 define('VC_PLUGIN_DIR', plugin_dir_path(__FILE__));
 define('VC_PLUGIN_URL', plugin_dir_url(__FILE__));