refactor(wireguard): name the compose host the mesh CLI gave no mesh

roles/svc-net-wireguard/vars/main.yml

@@ -11,6 +11,8 @@ WIREGUARD_ACTIVE_MESHES: >-
 
 WIREGUARD_MESH_NAMES: "{{ WIREGUARD_ACTIVE_MESHES.keys() | list | sort }}"
 
+WIREGUARD_MESHLESS_COMPOSE_HOST: "{{ DEPLOYMENT_MODE == 'compose' and WIREGUARD_MESH_NAMES | length == 0 }}"
+
 WIREGUARD_SPOKE_MESH_NAMES: >-
   {{ WIREGUARD_ACTIVE_MESHES | dict2items
      | rejectattr('value.is_hub')