v2-dev add prefix for proxy

[DeAlexPesh]

/app/next.config.mjs

PREFIX=/sub

const nextConfig = {
  trailingSlash: true,
  basePath: '${PREFIX}',
  assetPrefix: '${PREFIX}',
  async rewrites() {
    return [
      {
        source: '${PREFIX}/:path*',
        destination: '/:path*',
      },
    ]
  },
...