desktop-jovian: unify steam/jovian config across yarn + patiodeck

- modules/desktop-jovian.nix: shared Jovian deck-mode config (unfree
  predicate, jovian.steam, sddm, gamescope override, imports
  desktop-steam-update.nix)
- home/progs/steam-shortcuts.nix: declarative non-Steam shortcuts
  (Prism Launcher); add new entries here for all Jovian hosts
- hosts/yarn/default.nix: reduced to host-specific config only
- hosts/patiodeck/default.nix: same

hosts/patiodeck/home.nix

@@ -1,29 +1,8 @@
-{
-  pkgs,
-  inputs,
-  lib,
-  ...
-}:
+{ ... }:
 {
   imports = [
     ../../home/profiles/gui.nix
     ../../home/profiles/desktop.nix
-    inputs.json2steamshortcut.homeModules.default
+    ../../home/progs/steam-shortcuts.nix
   ];
-
-  services.steam-shortcuts = {
-    enable = true;
-    overwriteExisting = true;
-    steamUserId = lib.strings.toInt (
-      lib.strings.trim (builtins.readFile ../../secrets/home/steam-user-id)
-    );
-    shortcuts = [
-      {
-        AppName = "Prism Launcher";
-        Exe = "${pkgs.prismlauncher}/bin/prismlauncher";
-        Icon = "${pkgs.prismlauncher}/share/icons/hicolor/scalable/apps/org.prismlauncher.PrismLauncher.svg";
-        Tags = [ "Game" ];
-      }
-    ];
-  };
 }