Chat Guests, 'Only my chats' and Students with several chats (#93) - #101

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5, astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/