Add on-demand media URL refresh for expired MLS Grid tokens

MLS Grid media URLs expire after ~24 hours. Instead of running
scheduled syncs, this adds on-demand refresh when images are requested:

- Add is_url_expired() to parse expires timestamp from media URLs
- Add refresh_media_urls() to fetch fresh URLs from API for one listing
- Add get_property_media() API method using ListingId filter
- Image endpoint checks URL expiration before fetching
- If expired, refreshes URLs from API then proceeds with fetch

This is more efficient than scheduled full syncs because:
- Only refreshes URLs for listings actually being viewed
- Zero overhead for unviewed listings
- Scales naturally with traffic

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

wp-content/plugins/mls-by-hansonxyz/includes/class-mls-image-endpoint.php

@@ -137,6 +137,11 @@ class MLS_Image_Endpoint {
 
     /**
      * Get source image path, fetching from MLS if needed
+     *
+     * This method handles:
+     * 1. Returning cached local images if available
+     * 2. Checking if media URL has expired and refreshing if needed
+     * 3. Fetching images from MLS Grid on demand
      */
     private function get_source_image($listing_key, $index) {
         global $wpdb;
@@ -165,6 +170,30 @@ class MLS_Image_Endpoint {
             }
         }
 
+        // Check if the media URL has expired before trying to fetch
+        if ($this->media_handler->is_url_expired($media->media_url)) {
+            $this->logger->debug('Media URL expired, refreshing', array(
+                'listing_key' => $listing_key,
+                'index' => $index,
+            ));
+
+            // Refresh media URLs from API
+            if ($this->media_handler->refresh_media_urls($listing_key)) {
+                // Re-fetch the record with fresh URL
+                $media = $wpdb->get_row($wpdb->prepare(
+                    "SELECT * FROM {$db->media_table()}
+                     WHERE listing_key = %s AND media_order = %d
+                     LIMIT 1",
+                    $listing_key,
+                    $index
+                ));
+
+                if (!$media) {
+                    return null;
+                }
+            }
+        }
+
         // Fetch from MLS on demand
         $url = $this->media_handler->get_image_url($media, true);
         if (!$url) {