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.

docs/content/customization/asr.md

@@ -2,6 +2,11 @@
 
 语音识别（ASR）负责将用户音频实时转写为文本，供对话引擎理解。
 
+## 模式
+
+- `offline`：引擎本地缓冲音频后触发识别（适用于 OpenAI-compatible / SiliconFlow）。
+- `streaming`：音频分片实时发送到服务端，服务端持续返回转写事件（适用于 DashScope Realtime ASR）。
+
 ## 配置项
 
 | 配置项 | 说明 |
@@ -17,8 +22,8 @@
 - 客服场景建议开启热词并维护业务词表
 - 多语言场景建议按会话入口显式指定语言
 - 对延迟敏感场景优先选择流式识别模型
+- 当前支持提供商：`openai_compatible`、`siliconflow`、`dashscope`、`buffered`（回退）
 
 ## 相关文档
 
 - [语音配置总览](voices.md)
-