Implement DashScope ASR provider and enhance ASR service architecture

- Added DashScope ASR service implementation for real-time streaming.
- Updated ASR provider logic to support DashScope alongside existing providers.
- Enhanced runtime metadata resolution to include DashScope as a valid ASR provider.
- Modified configuration files and documentation to reflect the addition of DashScope.
- Introduced tests to validate DashScope integration and ASR service behavior.
- Refactored ASR service factory to accommodate new provider options and modes.

engine/providers/asr/openai_compatible.py

@@ -71,6 +71,7 @@ class OpenAICompatibleASRService(BaseASRService):
             on_transcript: Callback for transcription results (text, is_final)
         """
         super().__init__(sample_rate=sample_rate, language=language)
+        self.mode = "offline"
         
         if not AIOHTTP_AVAILABLE:
             raise RuntimeError("aiohttp is required for OpenAICompatibleASRService")