添加 GitHub Pages 文档与 CI 修复

新增功能：
- docs/ 目录：GitHub Pages 静态页面
  - index.html：项目主页
  - og-image.png/svg：社交分享图片
- tests/rustls_provider.rs：rustls CryptoProvider 集成测试
- rustls_provider 模块增强：
  - hash.rs：新增测试和文档
  - hmac.rs：新增测试和文档
  - kx.rs：新增测试和文档
  - sign.rs：新增测试和文档
  - verify.rs：新增测试和文档

CI 修复：
- rustls 依赖改为 git 源，避免本地路径依赖问题
- 简化 SM3 HMAC 流式测试，移除 alloc 依赖
- 移除未使用的 extern crate alloc
- 代码格式化

文档更新：
- README.md：添加 GitHub Pages 链接
- CHANGELOG.md：更新变更记录
- Cargo.toml：添加 dev-dependencies

README.md

@@ -7,7 +7,9 @@
 [![License](https://img.shields.io/crates/l/libsmx.svg)](LICENSE)
 [![MSRV](https://img.shields.io/badge/MSRV-1.83.0-blue.svg)](https://blog.rust-lang.org/2024/11/28/Rust-1.83.0.html)
 
-Pure-Rust, `#![no_std]` implementation of Chinese commercial cryptography standards with constant-time operations throughout.
+Pure-Rust, `#![no_std]` implementation of Chinese commercial cryptography standards (国密/GuoMi) with constant-time operations throughout. Designed for embedded systems, WASM, and production use.
+
+> **Security Notice**: This library has **not** been independently audited. While all secret-dependent operations are constant-time and `#![forbid(unsafe_code)]` is enforced, you should evaluate the risks before using it in production. Report vulnerabilities via [SECURITY.md](SECURITY.md) or email [kintai@foxmail.com](mailto:kintai@foxmail.com).
 
 | Algorithm | Standard | Description |
 |-----------|----------|-------------|
@@ -151,6 +153,7 @@ sm9_verify(msg, &h, &s, user_id, &sign_pub).unwrap();
 |---------|---------|-------------|
 | `alloc` | Yes | Enables `Vec`-returning APIs (SM2/SM9 encrypt/decrypt, SM4 modes) |
 | `std` | No | Enables `std::error::Error` impl and re-exports `rand_core/std` |
+| `rustls-provider` | No | Enables rustls `CryptoProvider` with RFC 8998 ShangMi TLS 1.3 cipher suites |
 
 For `no_std` without `alloc`:
 
@@ -159,6 +162,13 @@ For `no_std` without `alloc`:
 libsmx = { version = "0.3", default-features = false }
 ```
 
+With rustls TLS 1.3 provider:
+
+```toml
+[dependencies]
+libsmx = { version = "0.3", features = ["rustls-provider"] }
+```
+
 ## Benchmarks
 
 Measured on Linux x86_64 (single core). All operations are constant-time.
@@ -211,6 +221,12 @@ cargo bench
 
 > **Disclaimer**: This library has **not** been independently audited. See [SECURITY.md](SECURITY.md) for vulnerability reporting.
 
+## Contributing
+
+Bug reports, feature requests, and pull requests are welcome on [GitHub](https://github.com/kintaiW/libsmx).
+
+For **security vulnerabilities**, please do **not** open public issues. Instead, email [kintai@foxmail.com](mailto:kintai@foxmail.com) directly. See [SECURITY.md](SECURITY.md) for details.
+
 ## MSRV Policy
 
 The minimum supported Rust version is **1.83.0**. MSRV bumps are treated as minor version changes.