add attic cache

flake.nix

@@ -1,6 +1,18 @@
 {
   description = "Black Start essential infrastructure for cloud operations";
 
+  nixConfig = {
+    substituters = [
+      "https://nix-cache.dubyatp.xyz/duby"
+      "https://cache.nixos.org/"
+    ];
+
+    trusted-public-keys = [
+      "duby:IUVsFbQu499JOaHmUpi/mwhZEVQK7soFn7H6lD2/2T4="
+      "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+    ];
+  };
+
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
 
@@ -72,5 +84,7 @@
         };
       };
     };
+
+    packages.x86_64-linux.attic = nixpkgs.legacyPackages.x86_64-linux.attic-client;
   };
 }