fix(user): remove phantom system_status::get API (#377)

[foxzool]

Summary

• 删除 openlark-user 中飞书目录不存在的幻影 API SystemStatusResource::get() / SystemStatusGetRequest（畸形 URL，调用即失败）。
• system_status 资源仅保留 6 个真实构建器：list / create / patch / delete / batch_open / batch_close。
• 同步契约测试、文档注释与 CHANGELOG Breaking 条目（v0.18 线）。

Closes #377

Breaking

SystemStatusResource::get() 与 SystemStatusGetRequest 已移除。旧 get 对真实飞书本就 404；请改用 list() / SystemStatusListRequest。

Test plan

• cargo build --workspace --all-features
• cargo test -p openlark-user --all-features
• cargo test --workspace --all-features
• cargo clippy --workspace --all-targets --all-features -- -Dwarnings
• cargo clippy --workspace --all-targets --no-default-features -- -Dwarnings
• 全仓 grep：代码中无 SystemStatusGet / system_status::get 残留引用
• CI 绿灯

---

Note

Low Risk
Breaking only for code that called the already-nonfunctional get() API; no auth, data, or transport changes.

Overview
Breaking cleanup in openlark-user: removes the phantom Feishu system_status “get” surface that never matched a real API (malformed URL, would 404 on production).

SystemStatusResource::get(), SystemStatusGetRequest / SystemStatusGetResponse, and get.rs (including its wiremock test) are deleted. system_status is documented and wired as six builders only: list, create, patch, delete, batch_open, batch_close. The CHANGELOG moves this from a prior deprecation note to an explicit Breaking entry for the v0.18 line.

Migration: callers that used get() should use list() / SystemStatusListRequest—the old get was not viable against Feishu anyway.

^{Reviewed by Cursor Bugbot for commit cf1520a. Bugbot is set up for automated code reviews on this repo. Configure here.}

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