Add Nushell shell support and Nix flake packaging

Implement Nushell shell adapter (from nvbn/thefuck#1442) with alias
resolution, history management, and subprocess-based command execution.

Add uv2nix-based Nix flake for reproducible builds with Python 3.11,
pinned setuptools<71 for pkg_resources compatibility, and dev shell
with uv for local development.

flake.nix

@@ -0,0 +1,102 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+
+    pyproject-nix = {
+      url = "github:pyproject-nix/pyproject.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    uv2nix = {
+      url = "github:pyproject-nix/uv2nix";
+      inputs.pyproject-nix.follows = "pyproject-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    pyproject-build-systems = {
+      url = "github:pyproject-nix/build-system-pkgs";
+      inputs.pyproject-nix.follows = "pyproject-nix";
+      inputs.uv2nix.follows = "uv2nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+      pyproject-nix,
+      uv2nix,
+      pyproject-build-systems,
+    }:
+    let
+      workspace = uv2nix.lib.workspace.loadWorkspace { workspaceRoot = ./.; };
+
+      overlay = workspace.mkPyprojectOverlay {
+        sourcePreference = "wheel";
+      };
+    in
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          config.allowUnfree = true;
+        };
+
+        python = pkgs.python311;
+
+        # Override to provide fastentrypoints build-system dep
+        # (not in pyproject-build-systems because it's niche)
+        buildSystemOverride = final: prev: {
+          fastentrypoints = prev.fastentrypoints.overrideAttrs (old: {
+            nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [
+              (final.resolveBuildSystem { setuptools = [ ]; })
+            ];
+          });
+          thefuck = prev.thefuck.overrideAttrs (old: {
+            nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [
+              (final.resolveBuildSystem {
+                setuptools = [ ];
+                fastentrypoints = [ ];
+              })
+            ];
+          });
+        };
+
+        pythonSet =
+          (pkgs.callPackage pyproject-nix.build.packages {
+            inherit python;
+          }).overrideScope
+            (
+              nixpkgs.lib.composeManyExtensions [
+                pyproject-build-systems.overlays.wheel
+                overlay
+                buildSystemOverride
+              ]
+            );
+      in
+      {
+        packages.default = pythonSet.mkVirtualEnv "thefuck-env" workspace.deps.default;
+
+        apps.default = {
+          type = "app";
+          program = "${self.packages.${system}.default}/bin/thefuck";
+        };
+
+        devShell = pkgs.mkShell {
+          packages = with pkgs; [
+            uv
+            gh
+          ] ++ [ python ];
+          env = {
+            UV_NO_SYNC = "1";
+            UV_PYTHON = python.interpreter;
+            UV_PYTHON_DOWNLOADS = "never";
+          };
+        };
+      }
+    );
+}