Integrate empyrean configs into flake config

flake.nix

@@ -8,5 +8,9 @@
       system = "aarch64-linux";
       modules = [ ./machine/catacomb ];
     };
+    nixosConfiguration.empyrean = nixpkgs.lib.nixosSystem {
+      system = "x86_64-linux";
+      modules = [ ./machine/empyrean ];
+    };
   };
 }