fix(desktop): suppress hyprland default wallpaper flash on login

awww starts after the compositor, so hyprland painted its bundled
splash until the real wallpaper landed. Disable it via `misc`.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home.nix

@@ -465,6 +465,17 @@ in
         enabled = false;
       };
 
+      # Suppress Hyprland's built-in default wallpaper. The wallpaper here is
+      # driven by a userspace daemon (awww, see modules/media.nix) that only
+      # starts — and pushes the chosen image — once the compositor is up. Until
+      # then Hyprland paints its bundled splash, so on login it briefly shows
+      # before the real wallpaper replaces it. Disabling it leaves the plain
+      # background colour in that gap instead of a flash of unrelated art.
+      misc = {
+        force_default_wallpaper = 0;
+        disable_hyprland_logo = true;
+      };
+
       input = {
         kb_layout = "de";
         follow_mouse = 1;