fix: bump starlette to address a CVE - #308

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4, actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea, FedericoCarboni/setup-ffmpeg@37062fbf7149fc5578d6c57e08aed62458b375d6. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/