[REQUEST] Flake.nix

After updating nixos, you need to create ``format = "setuptools";`` in the section ```envycontrol = pkgs.python314Packages.buildPythonPackage```. Without this fix, an error appears: ```error: python3.14-envycontrol-3.5.2 does not configure a format. To build with setuptools as before, set pyproject = true and build-system = [ setuptools ].```
