Add support for Xfyun ASR and TTS services in the backend

- Introduce new Xfyun ASR and TTS services, enabling integration with iFlytek's voice recognition and synthesis capabilities.
- Update AssistantConfig model to include interface types for STT and TTS.
- Enhance credential testing to validate Xfyun credentials.
- Modify service factory to create Xfyun services based on configuration.
- Update README with new configuration details for Xfyun integration.
- Add new frontend components for visualizing audio streams and managing user interactions.

backend/models.py

@@ -31,6 +31,8 @@ class AssistantConfig(BaseModel):
     stt_language: str = ""
     tts_speed: float = 1.0
     realtimeModel: str = ""
+    stt_interface_type: str = "openai"
+    tts_interface_type: str = "openai"
 
     enableInterrupt: bool = True