Set default wallpaper to Attack-on-Titan-2

- Updated host variables files to select Attack-on-Titan-2.jpg and added
  rating comments.
- Simplified boot.nix by removing host‑specific imports and configuring
  limine via package, resolution, and branding color.
- Added limine target support in stylix with color, image, and tile
  scaling options.
- Removed the unused noctalia colors module and its import.
- Adjusted noctalia wallpaper settings to use config.stylix.image
  instead of a host import.

modules/home/stylix.nix

@@ -5,10 +5,10 @@
     vscode.enable = false;
     zed.enable = false;
     vesktop.enable = false;
+    noctalia-shell.enable = true;
     qt = {
       enable = true;
       platform = "qtct";
     };
-    noctalia-shell.enable = true;
   };
 }