refactor: use true common config and split rest

modules/nixos/client/login.nix

@@ -0,0 +1,23 @@
+{ lib, config, pkgs, ... }:
+{
+  options.swarselsystems.modules.login = lib.mkEnableOption "login config";
+  config = lib.mkIf config.swarselsystems.modules.login {
+    services.greetd = {
+      enable = true;
+      settings = {
+        initial_session.command = "sway";
+        default_session.command = ''
+          ${pkgs.greetd.tuigreet}/bin/tuigreet \
+            --time \
+            --asterisks \
+            --user-menu \
+            --cmd sway
+        '';
+      };
+    };
+
+    environment.etc."greetd/environments".text = ''
+      sway
+    '';
+  };
+}