发布 v0.3.0：rustls CryptoProvider 支持

新增功能：
- rustls CryptoProvider：完整 rustls 0.23.x 支持
  - SM3 Hash/Context trait 实现
  - SM3 HMAC trait 实现
  - SM4-GCM/CCM AEAD 密码套件
  - SM2 ECDHE 密钥交换
  - SM2 签名/验签算法
- SM3 流式 HMAC（HmacSm3）
- SM2 SPKI DER 编码
- SM2 DEFAULT_ID 常量

文档更新：
- README 依赖版本更新为 0.3
- CHANGELOG 添加 v0.3.0 变更记录
- SECURITY 更新版本支持表

Cargo.lock

@@ -422,13 +422,16 @@ checksum = "6800badb6cb2082ffd7b6a67e6125bb39f18782f793520caee8cb8846be06112"
 
 [[package]]
 name = "libsmx"
-version = "0.2.1"
+version = "0.3.0"
 dependencies = [
  "criterion",
  "crypto-bigint",
+ "getrandom",
  "hex",
  "rand 0.8.5",
  "rand_core 0.6.4",
+ "rustls",
+ "rustls-pki-types",
  "sm9_core",
  "subtle",
  "zeroize",
@@ -635,6 +638,25 @@ version = "0.8.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
 
+[[package]]
+name = "rustls"
+version = "0.24.0-dev.0"
+dependencies = [
+ "once_cell",
+ "rustls-pki-types",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "rustls-pki-types"
+version = "1.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be040f8b0a225e40375822a563fa9524378b9d63112f53e19ffff34df5d33fdd"
+dependencies = [
+ "zeroize",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"