chore: add license header for web

web/next.config.js

@@ -2,6 +2,9 @@
  * Run `build` or `dev` with `SKIP_ENV_VALIDATION` to skip env validation. This is especially useful
  * for Docker builds.
  */
+// Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+// SPDX-License-Identifier: MIT
+
 import "./src/env.js";
 
 /** @type {import("next").NextConfig} */