Add NixVirt support and GPU passthrough configuration

modules/desktop/niri/default.nix

@@ -139,9 +139,17 @@ let
       keyringExtra = lib.optionalString keyringEnable keyringNiriStartupKdl;
       extraConfigMerged = keyringExtra + rpi5Extra + (userExtra.extraConfig or "");
       windowRules = (base.window-rules or [ ]) ++ (userExtra.window-rules or [ ]);
+      userExtraNoSpecial = lib.removeAttrs userExtra [ "window-rules" "extraConfig" "binds" ];
+      mergedBinds =
+        (base.binds or { })
+        // (userExtra.binds or { })
+        // (niriCfg.extraBinds or { });
     in
     lib.recursiveUpdate base (
-      lib.removeAttrs userExtra [ "window-rules" "extraConfig" ]
+      userExtraNoSpecial
+      // {
+        binds = mergedBinds;
+      }
       // lib.optionalAttrs (windowRules != [ ]) {
         window-rules = windowRules;
       }
@@ -195,6 +203,15 @@ in
             Merged into shared defaults → `config.kdl` via wrapper-modules. Put raw KDL in `extraConfig`.
           '';
         };
+
+        extraBinds = lib.mkOption {
+          type = lib.types.attrsOf lib.types.anything;
+          default = { };
+          description = ''
+            Keybind overrides merged with shared defaults and `extraSettings.binds`.
+            Use this when multiple modules need to add binds without overwriting each other.
+          '';
+        };
       };
 
       config = lib.mkMerge [