Fix ASGI middleware assignment typing - #473

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684, actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065, astral-sh/setup-uv@f0ec1fc3b38f5e7cd731bb6ce540c5af426746bb. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/