Make /login only create rooms if matchmaking is enabled - #1118

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v3, actions/setup-dotnet@v3, actions/upload-artifact@v4, im-open/process-dotnet-test-results@v2.2.5, shogo82148/actions-setup-mysql@v1.40.0. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/