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DB backup polish (plan-task #764 Q3): - pg_dump now uses custom format (-Fc): compressed (much smaller on NFS) and restored via pg_restore. Artifact extension .sql → .dump; restore_db swaps psql -f for pg_restore -d. BackupRun.sql_path field name kept (it's just the db artifact path). - Reconcile the subprocess guardrails: the DB timeout was 720s with a stale 'Celery soft is 10 min' comment, but backup_db_task's soft limit is actually 1800s — so the bounded-kill fired 18 min early. Set DB=1700s / images=21000s, each just under its task's Celery soft limit so _run_bounded stays the primary guard (an NFS D-state hang defeats Celery's own SIGKILL). Real shrink of the DB is the #764 prune; this makes each dump smaller/faster on top of that. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>