Retrieves the current status of a schedule event import. Use this endpoint to poll for import completion after submitting a bulk import request.

When status is IMPORTED_WITH_ERRORS, a presigned S3 URL (valid for 10 minutes) is included in the response to download the error report CSV. The error report lists invalid rows and corresponding validation error messages for corrective re-import.

Poll this endpoint every 10-30 seconds after import submission until status is no longer IMPORTING.