niri overlay makes more sense in niri module

modules/niri/default.nix

@@ -1,4 +1,4 @@
-{ lib, config, pkgs, ... }: let
+{ inputs, lib, config, pkgs, ... }: let
   inherit (lib) mkIf;
   inherit (config) withNiri username;
 in {
@@ -7,6 +7,10 @@ in {
   ];
 
   config = mkIf withNiri {
+    nixpkgs.overlays = mkIf config.withNiri [
+      inputs.niri.overlays.niri
+    ];
+
     environment.sessionVariables = {
       NIXOS_OZONE_WL = "1";
     };

modules/nix/default.nix

@@ -1,8 +1,4 @@
 { inputs, ... }: {
-  imports = [
-    ./nixpkgs.nix
-  ];
-
   nix = {
     nixPath = ["nixpkgs=${inputs.nixpkgs}"];
     gc = {
@@ -16,4 +12,9 @@
     };
   };
 
+  nixpkgs = {
+    config = {
+      allowUnfree = true;
+    };
+  };
 }

modules/nix/nixpkgs.nix

@@ -1,13 +0,0 @@
-{ inputs, lib, config, ... }: let
-  inherit (lib) mkIf;
-in{
-  nixpkgs = {
-    overlays = mkIf config.withNiri [
-      inputs.niri.overlays.niri
-    ];
-
-    config = {
-      allowUnfree = true;
-    };
-  };
-}