ALTER TABLE `image_generations`
  DROP COLUMN `image_base64`,
  ADD COLUMN `hosted_image_url` VARCHAR(2048) NULL COMMENT 'Lsky 图床归档后的图片 URL' AFTER `image_url`,
  ADD COLUMN `hosted_response` JSON NULL COMMENT '完整 Lsky 图床上传接口响应' AFTER `upstream_response`;