✨ add Nix flake support

flake.nix

@@ -0,0 +1,86 @@
+{
+  description = "WebSocketReflectorX CLI flake";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems = [
+        "x86_64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+      forAllSystems = nixpkgs.lib.genAttrs systems;
+      version = "0.5.16";
+      assets = {
+        x86_64-linux = {
+          url = "https://github.com/XDSEC/WebSocketReflectorX/releases/download/${version}/wsrx-cli-${version}-linux-gnu-x86_64.tar.gz";
+          sha256 = "0fixr2hhj707yk5w7l505gdmhdb45pyhlsb45lps3794qihvqs4f";
+        };
+        x86_64-darwin = {
+          url = "https://github.com/XDSEC/WebSocketReflectorX/releases/download/${version}/wsrx-cli-${version}-macos-x86_64.zip";
+          sha256 = "1kfhgyna7i7259mapmz540favvdp1a2ac90ka08a1lf7blzgksk1";
+        };
+        aarch64-darwin = {
+          url = "https://github.com/XDSEC/WebSocketReflectorX/releases/download/${version}/wsrx-cli-${version}-macos-aarch64.zip";
+          sha256 = "0a3ylyhy2c0b1212dlw1q3z2r46kafkb22d9mmps381psvgbn038";
+        };
+      };
+    in
+    {
+      packages = forAllSystems (system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+          asset = assets.${system};
+          pkg = pkgs.stdenvNoCC.mkDerivation {
+            pname = "wsrx";
+            inherit version;
+            src = pkgs.fetchurl {
+              inherit (asset) url sha256;
+            };
+            nativeBuildInputs = [ pkgs.unzip ];
+            dontUnpack = true;
+            installPhase = ''
+              runHook preInstall
+
+              case "$src" in
+                *.tar.gz) tar -xzf "$src" ;;
+                *.zip) unzip -q "$src" ;;
+                *) echo "Unsupported archive: $src" >&2; exit 1 ;;
+              esac
+
+              bin_path="$(find . -type f -name wsrx | head -n1)"
+              install -Dm755 "$bin_path" "$out/bin/wsrx"
+
+              runHook postInstall
+            '';
+            meta = with pkgs.lib; {
+              description = "Controlled TCP-over-WebSocket forwarding tunnel";
+              homepage = "https://github.com/XDSEC/WebSocketReflectorX";
+              license = licenses.mit;
+              mainProgram = "wsrx";
+              platforms = builtins.attrNames assets;
+            };
+          };
+        in
+        {
+          default = pkg;
+          wsrx = pkg;
+        });
+
+      apps = forAllSystems (system:
+        let
+          pkg = self.packages.${system}.default;
+        in
+        {
+          default = {
+            type = "app";
+            program = "${pkg}/bin/wsrx";
+          };
+          wsrx = {
+            type = "app";
+            program = "${pkg}/bin/wsrx";
+          };
+        });
+    };
+}