refactor(sddm): replace noctalia theme with sddm-astronaut

Noctalia shell is no longer used; the only consumer left was the
SDDM login theme.

hosts/common/features/display/sddm.nix

@@ -1,7 +1,4 @@
 { pkgs, ... }:
-let
-  sddm-noctalia-theme = pkgs.callPackage ../../../../pkgs/sddm-noctalia-theme/package.nix { };
-in
 {
   services.xserver = {
     enable = true;
@@ -15,7 +12,7 @@ in
   services.displayManager.sddm = {
     enable = true;
     wayland.enable = true;
-    theme = "sddm-noctalia";
+    theme = "sddm-astronaut-theme";
     package = pkgs.kdePackages.sddm;
     extraPackages = with pkgs.kdePackages; [
       qtmultimedia
@@ -26,6 +23,6 @@ in
   };
 
   environment.systemPackages = with pkgs; [
-    sddm-noctalia-theme
+    sddm-astronaut
   ];
 }

pkgs/sddm-noctalia-theme/package.nix

@@ -1,33 +0,0 @@
-{ pkgs, ... }:
-
-pkgs.stdenv.mkDerivation {
-  pname = "sddm-noctalia-theme";
-  version = "1.0";
-
-  src = pkgs.fetchFromGitHub {
-    owner = "mahaveergurjar";
-    repo = "sddm";
-    rev = "noctalia";
-    sha256 = "sha256-e/gYI6znHXxlDCOVh4p265x3kO0nQUU897hCY1yEz88=";
-  };
-
-  installPhase = ''
-    mkdir -p $out/share/sddm/themes/sddm-noctalia
-    cp -r * $out/share/sddm/themes/sddm-noctalia/
-
-    # Patch for Qt6 SDDM greeter compatibility
-    # SDDM reads QtVersion from metadata.desktop to find the greeter binary;
-    # default is 5 (sddm-greeter), we need 6 (sddm-greeter-qt6)
-    substituteInPlace $out/share/sddm/themes/sddm-noctalia/metadata.desktop \
-      --replace-fail "Theme-Id=noctalia" "QtVersion=6
-    Theme-Id=noctalia"
-
-  '';
-
-  meta = with pkgs.lib; {
-    description = "Noctalia-themed SDDM login theme";
-    homepage = "https://github.com/mahaveergurjar/sddm/tree/noctalia";
-    license = licenses.gpl3;
-    platforms = platforms.linux;
-  };
-}