Update documentation to reflect rebranding from AI Video Assistant to Realtime Agent Studio (RAS)

- Changed site name and description in mkdocs.yml.
- Revised content in index.md to provide a comprehensive overview of RAS features and capabilities.
- Updated API reference and error documentation to replace AI Video Assistant with RAS.
- Modified deployment and getting started guides to align with the new branding.
- Enhanced quickstart instructions to specify RAS service requirements.

docs/content/api-reference/index.md

@@ -1,10 +1,10 @@
 # API 参考
 
-本节提供 AI Video Assistant 的完整 API 文档。
+本节提供 Realtime Agent Studio (RAS) 的完整 API 文档。
 
 ## API 概览
 
-AI Video Assistant 提供两种类型的 API：
+Realtime Agent Studio (RAS) 提供两种类型的 API：
 
 | API 类型 | 用途 | 协议 |
 |---------|------|------|