refactor: move from den based to flake-parts based

flake.nix

@@ -2,18 +2,17 @@
   description = "NixOS Configuration";
 
   inputs = {
-    den.url = "github:vic/den/v0.16.0";
     disko.url = "github:nix-community/disko";
+    flake-parts.follows = "lux-pkgs/flake-parts";
     home-manager.url = "github:nix-community/home-manager";
     import-tree.url = "github:vic/import-tree";
     niri.url = "github:sodiboo/niri-flake";
     nix-wrapper-modules.url = "github:BirdeeHub/nix-wrapper-modules";
     nixos-hardware.url = "github:NixOS/nixos-hardware/master";
     nixpkgs.url = "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
-    nixpkgs-stable.url = "github:NixOS/nixpkgs/nixos-25.11";
     noctalia.url = "github:noctalia-dev/noctalia-shell";
-    nvf.url = "github:notashelf/nvf";
     sops-nix.url = "github:Mic92/sops-nix";
+    treefmt-nix.url = "github:numtide/treefmt-nix";
 
     #vicinae.url = "github:vicinaehq/vicinae";
     vicinae-extensions.url = "github:vicinaehq/extensions";
@@ -21,18 +20,5 @@
     lux-pkgs.url = "git+ssh://gitea@orion/kiri/lux-pkgs";
   };
 
-  outputs =
-    inputs:
-    let
-      flake = (inputs.nixpkgs.lib.evalModules {
-        modules = [ (inputs.import-tree ./modules) ];
-        specialArgs.inputs = inputs;
-      }).config.flake;
-    in
-    flake
-    // {
-      formatter = inputs.nixpkgs.lib.genAttrs flake.den.systems (
-        system: inputs.nixpkgs.legacyPackages.${system}.nixfmt
-      );
-    };
+  outputs = inputs: inputs.flake-parts.lib.mkFlake { inherit inputs; } (inputs.import-tree ./modules);
 }