Add typing stubs (`.pyi` files) for PyO3-generated Python definitions

Even with https://github.com/channable/opsqueue/issues/8 resolved, type checkers will treat types that are exclusively defined via C bindings as `Any`. Typing stubs would fix this, but PyO3 currently does not generate them (https://github.com/PyO3/pyo3/issues/5137). Manually maintaining them would be annoying because it'd have to be kept in sync with the Rust definitions of the types, but it could still be valuable as a temporary solution.

首先定位通过 PyO3 暴露的 Rust 定义，并检查当前生成的 Python 定义是如何表示的。审查 PyO3 issue 5137 和现有的类型检查设置，然后确定 stubs 必须覆盖哪些导出类型和签名。完成意味着 stubs 描述了相关 binding，不再将这些类型保留为 Any，并且已记录如何与 Rust 定义一同维护。

由索引模型根据 Issue 内容生成。