clan-cli: get deploymentAddress from clan.networking

nixosModules/clanCore/flake-module.nix

@@ -3,6 +3,7 @@
     imports = [
       ./secrets
       ./zerotier.nix
+      ./networking.nix
       inputs.sops-nix.nixosModules.sops
       # just some example options. Can be removed later
       ./bloatware

nixosModules/clanCore/networking.nix

@@ -0,0 +1,15 @@
+{ config, lib, ... }:
+{
+  options.clan.networking = {
+    deploymentAddress = lib.mkOption {
+      description = ''
+        The target SSH node for deployment.
+
+        By default, the node's attribute name will be used.
+        If set to null, only local deployment will be supported.
+      '';
+      type = lib.types.nullOr lib.types.str;
+      default = "root@${config.networking.hostName}";
+    };
+  };
+}