Function cleanup_db_snapshot_cache 

pub async fn cleanup_db_snapshot_cache(resolved: &ResolvedDbSnapshots)

Remove cache tarballs after all consumers have finished extracting them, gated by the ZOMBIE_RM_TGZ_AFTER_EXTRACT env var. Best-effort: errors are logged and swallowed (cleanup must never fail spawn).

Must be called only after every node that consumes the cache has completed its initialize_db_snapshot — otherwise concurrent readers will hit ENOENT.