Deletes a specific pay rate entry for a user. The pay rate is identified by the user ID and effective date. This operation cannot be undone. The system validates that the effective date does not affect any approved or locked timesheet days. If the user has any approved or locked days on or after this effective date, the delete request will fail with error code HAS_LOCKED_DAYS. You cannot delete pay rates that are currently being used for finalized payroll calculations. Additionally, at least one pay rate must remain for each user (if required by company policy).