Add Steam Deck (nix-deck) configuration with Jovian-NixOS and remote building

- Add Jovian-NixOS integration for Steam Deck hardware support
- Create nix-deck machine configuration with SteamOS role
- Add jovian-compat.nix for NixOS 25.05 compatibility (remove in 25.11+)
- Create remote-build role for distributed builds
- Configure zix790prors as build host
- Configure nix-book and nix-deck to use remote builder with fallback
- Add comprehensive setup documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

roles/jovian-compat.nix

@@ -0,0 +1,43 @@
+{ lib, config, ... }:
+
+# Compatibility shim to provide services.logind.settings for NixOS 25.05
+# This allows Jovian-NixOS to work with stable NixOS
+# REMOVE THIS FILE when upgrading to NixOS 25.11 or later
+
+with lib;
+
+let
+  nixosVersion = config.system.nixos.release;
+  isCompatibleVersion = versionOlder nixosVersion "25.11";
+in
+{
+  options.services.logind.settings = mkOption {
+    type = types.attrsOf (types.attrsOf types.anything);
+    default = {};
+    description = "systemd-logind configuration. See logind.conf(5) for available options.";
+  };
+
+  config = mkMerge [
+    {
+      assertions = [
+        {
+          assertion = isCompatibleVersion;
+          message = ''
+            The Jovian compatibility shim (roles/jovian-compat.nix) is only needed for NixOS 25.05 and earlier.
+            You are running NixOS ${nixosVersion}.
+            Please remove 'roles/jovian-compat.nix' from your flake.nix imports.
+          '';
+        }
+      ];
+    }
+    (mkIf (config.services.logind.settings != {}) {
+      # Convert the settings to extraConfig format for older NixOS
+      services.logind.extraConfig = let
+        mkSection = section: settings:
+          "[${section}]\n" +
+          (concatStringsSep "\n" (mapAttrsToList (k: v: "${k}=${toString v}") settings));
+      in
+        concatStringsSep "\n\n" (mapAttrsToList mkSection config.services.logind.settings);
+    })
+  ];
+}