- fix params lost in RabbitMQ transit by threading them through PublishTask/PublishTaskWithRetry
- fix UpdateTaskErrorInfo not setting status=FAILED on async_task
- fix UpdateAsyncTaskResultWithError silently skipping when no result row exists (UPDATE → upsert)
- sync task failure to async_task_result in updateTaskWithError
- remove taskType from AsyncTaskHandler.Execute interface; rename TaskHandler → AsyncTaskHandler
- replace CompositeHandler with direct factory.GetHandler dispatch via worker.dispatch()
- use constructors (NewXxxHandler) for handler registration instead of zero-value literals
- consolidate TaskType/TaskStatus/UnifiedTaskType into task/types.go; delete types_v2.go
- extract BaseTask/TaskParams into task/base_task.go
douxu