feat: initial TTS support

Will be added once `llama.cpp`'s TTS APIs are finalized and [Orpheus](https://github.com/canopyai/Orpheus-TTS) ([issue](https://github.com/ggml-org/llama.cpp/issues/12476)) or [SparkTTS](https://github.com/SparkAudio/Spark-TTS) ([issue](https://github.com/ggml-org/llama.cpp/issues/12495)) models are supported.