Rebuild complete HTTP API references from SDK/protocol mappings and restore discoverability + Try-It usability.

Scope:

1. Endpoint inventory and mapping (HTTP method + path + SDK method)
2. Parameter/request/response schema normalization
3. Auth/signature/error-code cross-linking
4. Multi-language parity (en/zh-CN/zh-HK)
5. Navigation and landing page optimization for API Reference
6. Validation pass with sample requests and consistency checks