Include ckpool volume in backup and restore

The backup only covered /root/.kamado (DB, config, TLS certs) but
missed /root/.ckpool which holds miner/worker state, pool status,
and ckpool logs. Without it a restore would lose all per-user and
per-worker statistics.

manifest.yaml

@@ -131,9 +131,11 @@ backup:
       - create
       - /mnt/backup
       - /root/.kamado
+      - /root/.ckpool
     mounts:
       BACKUP: /mnt/backup
       main: /root/.kamado
+      ckpool: /root/.ckpool
   restore:
     type: docker
     image: compat
@@ -144,9 +146,11 @@ backup:
       - restore
       - /mnt/backup
       - /root/.kamado
+      - /root/.ckpool
     mounts:
       BACKUP: /mnt/backup
       main: /root/.kamado
+      ckpool: /root/.ckpool
 
 actions:
   stratum-smoke-test: