fix: record error message and backtrace when job expires

[SAY-5]

Closes #438.

Que.execute :expire_job previously took only the job id, so when error_count > maximum_retry_count the row was marked expired_at but last_error_message and last_error_backtrace stayed nil. The retry path already records both via :set_error, so jobs that exhaust retries lost the diagnostic info from their final failure.

The :expire_job SQL now also takes the error message and backtrace and writes them with COALESCE, so callers of the public Que::JobMethods#expire that have no que_error (manual expiration) still preserve any previously recorded error. Worker#work_job and JobMethods#expire both pass the error through when one is present.