feat: add nix flake package

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1780030872,
+        "narHash": "sha256-u6WU/yd/o8iYQrHX3RAwO1hYa3LkoSL+WNQD0rJfJZQ=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e9a7635a57597d9754eccebdfc7045e6c8600e6b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,50 @@
+{
+  description = "ihtc — SNI-based DPI bypass via TLS ClientHello fragmentation";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      forAllSystems = nixpkgs.lib.genAttrs [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+
+      mkPackage = system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+          version = builtins.substring 0 8 (self.lastModifiedDate or "19700101");
+        in
+        pkgs.buildGoModule {
+          pname = "ihtc";
+          version = "0.1.0-${version}";
+          src = ./.;
+          vendorHash = null;
+          meta = with pkgs.lib; {
+            description = "SNI-based DPI bypass via TLS ClientHello fragmentation";
+            homepage = "https://github.com/kreatoo/ihtc";
+            license = licenses.mit;
+            mainProgram = "ihtc";
+            platforms = platforms.unix;
+          };
+        };
+    in
+    {
+      packages = forAllSystems (system: {
+        default = mkPackage system;
+        ihtc = mkPackage system;
+      });
+
+      devShells = forAllSystems (system:
+        let pkgs = import nixpkgs { inherit system; };
+        in {
+          default = pkgs.mkShell {
+            buildInputs = with pkgs; [ go gopls gotools ];
+          };
+        });
+    };
+}