Add shell.nix, requirements

requirements.txt

@@ -0,0 +1 @@
+tldextract

shell.nix

@@ -0,0 +1,15 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    python312
+    python312Packages.tldextract
+    sing-box
+  ];
+
+  shellHook = ''
+    echo "Environment ready!"
+    echo "Python version: $(python --version)"
+    echo "sing-box version: $(sing-box version 2>/dev/null || echo 'not available')"
+  '';
+}