Add API-reference HTTP endpoint catalog from Rust SDK mapping

[xiaobo-gaga]

This PR adds missing direct HTTP API information under api-reference, based on the real SDK implementation in longportapp/openapi Rust source.

What’s added

• New page in 3 locales:
  • docs/en/docs/api-reference/http-endpoints.md
  • docs/zh-CN/docs/api-reference/http-endpoints.md
  • docs/zh-HK/docs/api-reference/http-endpoints.md
• Added link from each how-to-access-api page to this HTTP endpoint catalog.

Data source (verified)

Mapped from:

• https://github.com/longportapp/openapi/blob/main/rust/src/quote/context.rs
• https://github.com/longportapp/openapi/blob/main/rust/src/trade/context.rs
• https://github.com/longportapp/openapi/blob/main/rust/src/config.rs

Includes endpoint + HTTP method pairs currently used by SDK HTTP client.

Scope

This is the first completion step for “SDK docs lacking direct API URL”.
Next PRs can continue filling HTTP method/path directly into each individual API page where currently only SDK examples are shown.

[xiaobo-gaga]

@huacnlee 已按你的要求把 改为“每个 API 一个文件”的结构（参考 Mintlify 风格）。\n\n本次更新（en）：\n- 新增目录：\n- 22 个 endpoint 页面（每页包含 Method / URL / Base URL / SDK source）\n- 改为索引页（链接到每个 endpoint 子页）\n\ncommit: 7b3afcf\n\n如果你确认这个结构 OK，我下一步按同样方式同步 zh-CN / zh-HK。

[xiaobo-gaga]

补充更正：上一条评论里因 shell 转义导致文件名显示异常。实际变更已正确提交到 commit 0242329：将 en 的 HTTP endpoints 拆分为每个 API 一个文件，并由索引页统一链接。

[huacnlee]

@xiaobo-gaga 继续，还不够细化，不够清晰

[xiaobo-gaga]

@huacnlee 收到，我继续细化（按你要的 Mintlify 风格）：\n\n下一批会把每个 endpoint 补完整：\n1) Parameters 全部用 Table（Query/Header/Body/Path 分开）\n2) Response fields 用 Table（字段类型/说明）\n3) cURL 请求示例改为可直接跑\n4) Response 示例改为实际调用结果（能实测的用真实数据，受权限限制的补真实错误响应）\n\n我会先从 watchlist + quote + asset/account 三组开始，分批提交，便于 review。