Add US geo data tables, filter bounds API, and URL hash state management

- Add mls_geo_cities and mls_geo_zipcodes tables with 29,880 cities and 33,144 zip codes
- Add get_filter_bounds() method to reposition map when filters don't intersect current view
- Move all URL state (filters, page, scroll, map position) to hash to avoid WordPress 404s
- Add filter bounds AJAX endpoint for map repositioning on filter change

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

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

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

@@ -31,6 +31,8 @@ define('MLS_TABLE_SYNC_STATE', 'mls_sync_state');
 define('MLS_TABLE_RATE_LIMITS', 'mls_rate_limits');
 define('MLS_TABLE_SYNC_LOG', 'mls_sync_log');
 define('MLS_TABLE_MEDIA_LOG', 'mls_media_log');
+define('MLS_TABLE_GEO_CITIES', 'mls_geo_cities');
+define('MLS_TABLE_GEO_ZIPCODES', 'mls_geo_zipcodes');
 
 // HomeProz office MLS ID for identifying our listings
 define('MLS_HOMEPROZ_OFFICE_ID', 'NST253235');
@@ -390,6 +392,20 @@ function mls_get_property_count($args = array()) {
     return $plugin->get_query()->get_count($args);
 }
 
+/**
+ * Get geographic bounds for filtered properties
+ *
+ * @param array $args Filter arguments
+ * @return array|null Bounds with sw_lat, sw_lng, ne_lat, ne_lng
+ */
+function mls_get_filter_bounds($args = array()) {
+    $plugin = mls_plugin();
+    if (!$plugin->get_query()) {
+        return null;
+    }
+    return $plugin->get_query()->get_filter_bounds($args);
+}
+
 /**
  * Get all images for a listing (on-demand fetching)
  *