update flake.nix

Author: wrjade

flake.nix

@@ -19,6 +19,34 @@
       in {
         formatter = pkgs.alejandra;
 
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            # Nix development tools
+            alejandra
+            nixpkgs-fmt
+            
+            # Docker tools
+            dockerTools
+            
+            # Python development tools
+            python312
+            uv
+            
+            # Build tools
+            gnutar
+            gzip
+            curl
+          ];
+          
+          shellHook = ''
+            echo "🐍 Python Docker Runner Development Environment"
+            echo "Available commands:"
+            echo "  nix build .#docker-image  - Build Docker image"
+            echo "  nix fmt                   - Format Nix files"
+            echo ""
+          '';
+        };
+        
         packages = {
           # Docker image package for CI/CD
           docker-image = import ./docker.nix {inherit pkgs;};