Add WebP conversion and garbage collection to MLS plugin

Image handling improvements:
- Convert PNG and images >500KB to WebP format
- Resize images wider than 1600px maintaining aspect ratio
- Check for .webp version before falling back to original
- WebP quality set to 80 (equivalent to JPEG 90%)

Garbage collection for disk space management:
- New MLS_Garbage_Collector class runs after each sync
- Only active when MLS_GC_DISK_THRESHOLD defined in wp-config
- Deletes image directories older than 24 hours, oldest first
- Stops when free space reaches 5GB or 2GB deleted per run
- Protects recently accessed images from deletion

Documentation:
- Added Garbage Collection section to README
- Updated Features list and File Structure

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

wp-content/plugins/mls-by-hansonxyz/mls-by-hansonxyz.php

@@ -63,6 +63,7 @@ final class MLS_Plugin {
     private $image_endpoint;
     private $query;
     private $cluster;
+    private $garbage_collector;
 
     /**
      * Get single instance
@@ -98,6 +99,7 @@ final class MLS_Plugin {
         require_once MLS_PLUGIN_DIR . 'includes/class-mls-query.php';
         require_once MLS_PLUGIN_DIR . 'includes/class-mls-cluster.php';
         require_once MLS_PLUGIN_DIR . 'includes/class-mls-geo-validator.php';
+        require_once MLS_PLUGIN_DIR . 'includes/class-mls-garbage-collector.php';
 
         // Activation/Deactivation
         require_once MLS_PLUGIN_DIR . 'includes/class-mls-activator.php';
@@ -149,6 +151,7 @@ final class MLS_Plugin {
         );
         $this->query = new MLS_Query($this->db);
         $this->cluster = new MLS_Cluster($this->db);
+        $this->garbage_collector = new MLS_Garbage_Collector($this->logger);
 
         // Register AJAX handlers
         add_action('wp_ajax_mls_get_clusters', array($this, 'ajax_get_clusters'));
@@ -247,6 +250,13 @@ final class MLS_Plugin {
         return $this->cluster;
     }
 
+    /**
+     * Get Garbage Collector instance
+     */
+    public function get_garbage_collector() {
+        return $this->garbage_collector;
+    }
+
     /**
      * AJAX handler for getting map clusters
      */