Make sparky a NFS backup instead of desktop.

hosts/zippy/default.nix

@@ -6,7 +6,6 @@
     ../../common/cluster-member.nix  # Consul + storage clients
     ../../common/nomad-worker.nix     # Nomad client (runs jobs)
     # NOTE: zippy is NOT a server - no nomad-server.nix import
-#    ../../common/ethereum.nix
     ../../common/nfs-services-server.nix  # NFS server for /data/services
     # To move NFS server role to another host:
     # 1. Follow procedure in docs/NFS_FAILOVER.md
@@ -24,6 +23,8 @@
   networking.hostName = "zippy";
   services.tailscaleAutoconnect.authkey = "tskey-auth-ktKyQ59f2p11CNTRL-ut8E71dLWPXsVtb92hevNX9RTjmk4owBf";
 
-  # NFS server configuration: replicate to c1 as standby
-  nfsServicesServer.standbys = [ "c1" ];
+  nfsServicesServer.standbys = [
+    "c1"
+    "sparky"
+  ];
 }