feat: use flake-parts and auto-generate nixosConfigurations for all hosts

flake.nix

@@ -6,6 +6,9 @@
   };
 
   outputs = inputs: inputs.flake-parts.lib.mkFlake { inherit inputs; }  {
+    systems = [
+      "x86_64-linux"
+    ];
     imports = [
       ./hosts
     ];

hosts/default.nix

@@ -6,15 +6,15 @@ let
     lib.filterAttrs isDirectory (builtins.readDir ./.)
   );
   hosts = lib.genAttrs hostNames (name: {
-    imports = [
+    modules = [
       (./. + "/${name}")
     ];
   });
 in 
 {
-  nixosConfigurations = lib.mapAttrs (host: hostConfig: lib.nixosSystem {
+  flake.nixosConfigurations = lib.mapAttrs (host: hostConfig: lib.nixosSystem {
+    inherit (hostConfig) modules;
     system = "x86_64-linux";
-    modules = hostConfig;
     specialArgs = { inherit inputs; };
   }) hosts;
 }