clan-cli: initialize python project from template

clan-cli: remove unnecessary unit test file

clan-cli: fix shell.nix too stateful

clan-cli: remove conftest.py

clan-cli: fix flake-module.nix

pkgs/clan-cli/flake-module.nix

@@ -0,0 +1,10 @@
+{
+  perSystem = {pkgs, ...}: let
+    pyproject = builtins.fromTOML (builtins.readFile ./pyproject.toml);
+    name = pyproject.project.name;
+    package = pkgs.callPackage ./default.nix {};
+  in {
+    # packages.${name} = package;
+    checks.python-template = package.tests.check;
+  };
+}