fix(g18-next): limit gitea registration

hosts/g18-next/configuration.nix

@@ -78,6 +78,10 @@ in
         PROXY_URL = "http://192.168.255.1:20171";
         PROXY_HOSTS = "github.com";
       };
+      service = {
+        ENABLE_CAPTCHA = true;
+        REGISTER_MANUAL_CONFIRM = true;
+      };
     };
   };
   systemd.sockets.gitea.listenStreams = [ "22" ];