-- 任务归档 (T-ARC): 项目自动归档档位 + 任务归档三字段与查询索引
ALTER TABLE `Project` ADD COLUMN `autoArchive` VARCHAR(8) NOT NULL DEFAULT 'never';
ALTER TABLE `Task` ADD COLUMN `archived` BOOLEAN NOT NULL DEFAULT false;
ALTER TABLE `Task` ADD COLUMN `archivedAt` DATETIME(3) NULL;
ALTER TABLE `Task` ADD COLUMN `archiveSource` VARCHAR(8) NULL;
ALTER TABLE `Task` ADD INDEX `idx_task_project_archived` (`projectId`, `archived`, `archivedAt`);
ALTER TABLE `Task` ADD INDEX `idx_task_project_status_arch` (`projectId`, `status`, `archived`);