feat(audio): Add managed TTS engine service with OpenAI /v1/audio/speech compatibility - #21

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

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Calls to methods which accept CancellationToken should use TestContext.Current.CancellationToken to allow test cancellation to be more responsive. (https://xunit.net/xunit.analyzers/rules/xUnit1051)

Dereference of a possibly null reference.