Add Ultravox service (#1)

Adds support for using Ultravox Realtime as a speech-to-speech service.

Also removes the deprecated Ultravox speech-to-text vllm model integration to avoid confusion.

.github/workflows/python-compatibility.yaml

@@ -50,7 +50,6 @@ jobs:
         run: |
           uv sync --group dev --all-extras \
             --no-extra krisp \
-            --no-extra ultravox \
             --no-extra local-smart-turn \
             --no-extra moondream \
             --no-extra mlx-whisper