v3.4.143

Fix backfill jobs stranded when WordPress collapses duplicate cron events.

queue_backfill() schedules one wp_schedule_single_event() per job it inserts, but when a variable-product save queues jobs for several variations in the same request, WordPress silently de-duplicates the same-second single events sharing the hook/args — only one survives. process_backfill() previously only rescheduled itself when the claimed job had more batches to run, so any other pending job left without a surviving event stayed pending indefinitely with nothing to pick it up. process_backfill() now checks for remaining pending jobs and reschedules a follow-up run whenever it finishes handling the job it claimed.