backup: harden lifecycle fencing and skip near-empty archives

backup-node.sh now stops services, fences COMPOSE_FILE during backup, and
restores via EXIT trap; consumers skip <1MB .tar.zst artifacts so purged-
volume junk cannot shadow real backups.

Co-authored-by: Cursor <cursoragent@cursor.com>

list-restorable.sh

@@ -12,6 +12,7 @@
 #   ./list-restorable.sh <network> --all <chain>  # --all can be in any position
 
 dir="$(dirname "$0")"
+source "$dir/volume-utils.sh"
 registry_file="${dir}/compose_registry.json"
 backup_dir="/backup"
 
@@ -122,7 +123,7 @@ while IFS= read -r entry; do
     while IFS= read -r volume; do
         volume_name="rpc_${volume}"
         # Look for backup files matching pattern: rpc_${volume}-[0-9]*G.tar.zst
-        backup_file=$(ls -1 "$backup_dir"/"${volume_name}"-[0-9]*G.tar.zst 2>/dev/null | sort | tail -n 1)
+        backup_file=$(select_newest_local_backup "$backup_dir" "$volume_name")
         
         if [ -z "$backup_file" ]; then
             all_backups_exist=false