feat(task): introduce task timeout configuration and cleanup unfinished tasks

- Added TaskTimeoutMinutes constant to configure the timeout duration for asynchronous tasks.
- Implemented sweepTimedOutTasks function to identify and handle unfinished tasks that exceed the timeout limit, marking them as failed and processing refunds if applicable.
- Enhanced task polling loop to include the new timeout handling logic, ensuring timely cleanup of stale tasks.

constant/env.go

@@ -16,6 +16,7 @@ var NotificationLimitDurationMinute int
 var GenerateDefaultToken bool
 var ErrorLogEnabled bool
 var TaskQueryLimit int
+var TaskTimeoutMinutes int
 
 // temporary variable for sora patch, will be removed in future
 var TaskPricePatches []string