refactor: restructure config files

modules/capabilities/sddm.nix

@@ -0,0 +1,21 @@
+{
+  flake.modules.nixos.sddm =
+    {
+      pkgs,
+      ...
+    }:
+    {
+      services.displayManager.sddm = {
+        enable = true;
+        enableHidpi = true;
+        wayland.enable = true;
+        wayland.compositor = "kwin";
+        theme = "${
+          pkgs.sddm-astronaut.override { embeddedTheme = "purple_leaves"; }
+        }/share/sddm/themes/sddm-astronaut-theme";
+        extraPackages = with pkgs; [
+          kdePackages.qtmultimedia
+        ];
+      };
+    };
+}