add nix config to base config

common/core.nix

@@ -6,4 +6,19 @@
   programs.nix-ld.enable = true;
   security.sudo.wheelNeedsPassword = false;
   system.stateVersion = "25.11";
+
+  nix = {
+    settings = {
+      experimental-features = ["nix-command" "flakes"];
+      auto-optimise-store = true;
+      trusted-users = ["@wheel"];
+      substituters = [
+        "https://nix-cache.dubyatp.xyz/duby"
+      ];
+      trusted-public-keys = [
+        "duby:IUVsFbQu499JOaHmUpi/mwhZEVQK7soFn7H6lD2/2T4="
+        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+      ];
+    };
+  };
 }