flake: add nixpkgs input url

flake.nix

@@ -1,5 +1,8 @@
 {
-  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.05";
+  };
 
   outputs = {
     self,
@@ -42,6 +45,9 @@
         trivium = overlay;
       };
 
+      homeManagerModules.default = ./hm;
+      nixosModules.default = ./nixos;
+
       lib = {
         mkSystemFlake = {
           flakes,
@@ -151,7 +157,7 @@
                 hostConfig = platform:
                   nixosSystem {
                     modules = [
-                      ./nixos
+                      self.nixosModules.default
                       nixosSourcePath
                       platform
                     ];
@@ -177,7 +183,7 @@
                     };
 
                     modules = [
-                      ./hm
+                      self.homeManagerModules.default
                       hmSourcePath
                       platform
                       registry