-- AlterTable: 添加系统维护通知字段
ALTER TABLE "system_settings" ADD COLUMN IF NOT EXISTS "maintenance_enabled" BOOLEAN NOT NULL DEFAULT false;
ALTER TABLE "system_settings" ADD COLUMN IF NOT EXISTS "maintenance_message" TEXT;
ALTER TABLE "system_settings" ADD COLUMN IF NOT EXISTS "maintenance_start_time" TIMESTAMP(3);
ALTER TABLE "system_settings" ADD COLUMN IF NOT EXISTS "maintenance_end_time" TIMESTAMP(3);