back to kde+karousel, niri was cool, but it wasn't kde

aspects/desktop/kde.nix

@@ -33,6 +33,10 @@
           ];
           config.common.default = "*";
         };
+        environment.systemPackages = with pkgs; [
+          kdePackages.karousel
+          kde-rounded-corners
+        ];
         programs.kdeconnect.enable = true;
       };