Allow only exposing services over Tailscale

This works using public DNS, so doesn't need Tailscale's magic DNS to override my local.

terraform/context.tf

@@ -2,6 +2,8 @@ resource "local_file" "hosts" {
   content = yamlencode({
     vps_hosts : {
       casey_ip : linode_instance.casey.ip_address,
+      private_ipv6_marker : local.private_ipv6_marker,
+      private_ipv6_range : local.private_ipv6_range,
       walker_ip : vultr_instance.walker.main_ip,
     }
   })