Legion: temp revert username change, enable key-based root login only

flake.nix

@@ -171,6 +171,7 @@
 
       Legion = systemConfig {
         hostName = "Legion";
+        user = "xenia";
         systemModules = [
           ./services/nix-serve.nix
           ./services/caddy.nix

services/sshd.nix

@@ -4,7 +4,7 @@
     ports = [22];
     settings = {
       UseDns = true;
-      PermitRootLogin = "no";
+      PermitRootLogin = "without-password";
       PasswordAuthentication = false;
       GatewayPorts = "yes";
       LogLevel = "VERBOSE";