build: add nix package

.gitignore

···
 /target
+result

default.nix

···
+{
+  rustPlatform,
+  ...
+}:
+rustPlatform.buildRustPackage {
+  pname = "clickee-proxy";
+  version = "main";
+
+  src = ./.;
+
+  cargoLock.lockFile = ./Cargo.lock;
+}

flake.lock

···
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1757873102,
+        "narHash": "sha256-kYhNxLlYyJcUouNRazBufVfBInMWMyF+44xG/xar2yE=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "88cef159e47c0dc56f151593e044453a39a6e547",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

···
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+
+  outputs = inp: let
+    l = inp.nixpkgs.lib;
+    systems = ["x86_64-linux"];
+    forPkgs = f: l.genAttrs systems (s: f inp.nixpkgs.legacyPackages.${s});
+  in {
+    packages = forPkgs (pkgs: rec {
+      clickee-proxy = pkgs.callPackage ./default.nix {};
+      default = clickee-proxy;
+    });
+  };
+}