fix(2meet-data-optimizer-hivepress-addon): map bookings hot field to hp_quantity

- hivepress-bookings has no guests field; the places booked are stored as
  hp_quantity (only when "Allow multiple places" is enabled)
- Verified against hivepress-bookings 1.5.5: start_time / end_time were
  already correct and stay unchanged

Verify: vendor/bin/phpunit --filter test_on_register_fields_uses_real_booking_meta_keys;
  addon unit 155 OK, integration 57 OK
PR: PR-009

includes/hivepress/adapters/class-tmdo-hivepress-bookings-adapter.php

@@ -10,7 +10,8 @@
  *
  *   start_time / end_time   → unix timestamp range queries (hot)
  *   status                  → enum filter (hot)
- *   guests                  → numeric count (hot for slot-availability)
+ *   quantity                → places booked, hp_quantity (hot for slot-availability;
+ *                             only written when "Allow multiple places" is on)
  *   listing                 → post_parent (already a posts column)
  *
  * Hot-zone target: `wp_wpdo_hot_hp_booking` with covering indexes on
@@ -91,10 +92,10 @@ if ( ! class_exists( 'TMDO_HivePress_Bookings_Adapter' ) ) {
 					),
 					array(
 						'post_type' => 'hp_booking',
-						'meta_key'  => 'hp_guests',
+						'meta_key'  => 'hp_quantity',
 						'zone'      => 'hot',
 						'data_type' => 'int(11) NOT NULL DEFAULT 0',
-						'column'    => 'hp_guests',
+						'column'    => 'hp_quantity',
 						'indexed'   => false,
 					),
 				)