[
  {
    "type": "alter_table",
    "description": "Add delivery status tracking fields to seller_marketing_queue table",
    "database": "kiosk_buykiosk",
    "check_query": "SHOW COLUMNS FROM seller_marketing_queue WHERE Field = 'delivery_status'",
    "sql": "ALTER TABLE `seller_marketing_queue` ADD COLUMN `delivery_status` enum('unknown','sent','delivered','failed','undelivered') DEFAULT 'unknown' COMMENT 'Provider delivery status', ADD COLUMN `delivery_timestamp` timestamp NULL DEFAULT NULL COMMENT 'When delivery status was received', ADD COLUMN `delivery_error_code` varchar(50) DEFAULT NULL COMMENT 'Provider error code if delivery failed', ADD COLUMN `delivery_error_message` text DEFAULT NULL COMMENT 'Provider error message if delivery failed'"
  }
]