nanopos: add netns

- Adds nanopos to netns-isolation.services
- Adds cfg.enforceTor and extraArgs to bring nanopos in line with other
  services
- Adds charged-url option to allow using nanopos with network
  namespaces.
- Modularizes nginx so webindex can be used without nanopos.
- Adds host option (defaults to localhost) as target of hidden service
- Removes unnecessary after

modules/presets/secure-node.nix

@@ -129,6 +129,8 @@ in {
 
     services.lightning-charge.enforceTor = true;
 
+    services.nanopos.enforceTor = true;
+
     services.nix-bitcoin-webindex.enforceTor = true;