Add worf keys and zfs-exporter

hosts/voyager/services/metrics/prometheus.nix

@@ -55,6 +55,12 @@ in {
           }
         ];
       }
+      {
+        job_name = "zfs";
+        static_configs = [
+          { targets = ["127.0.0.1:${toString config.services.prometheus.exporters.zfs.port}"]; }
+        ];
+      }
     ];
   };
 }