重构：RustCrypto 兼容接口

主要变更：
- 新增 sm2/、sm3/、sm4/ 独立 crate，实现 RustCrypto traits
  - sm2：实现 signature、elliptic-curve traits
  - sm3：实现 digest、crypto-common traits
  - sm4：实现 cipher、aead traits
- 新增 fuzz/ 模糊测试目标
- 新增 tests/sm2_proptest.rs 属性测试
- 重构 src/sm4/ 使用 RustCrypto AEAD traits
- 更新 CI 工作流支持多 crate 测试
- 更新 .gitignore 忽略 fuzz/target/

Cargo.toml

@@ -1,3 +1,22 @@
+# ── Workspace 配置 ──────────────────────────────────────────────────────────
+[workspace]
+resolver = "2"
+members = [
+    ".",      # libsmx (现有单体 crate，保持向后兼容)
+    "sm2",    # SM2 独立 crate（实现 signature::Signer/Verifier）
+    "sm3",    # SM3 独立 crate（实现 digest::Digest）
+    "sm4",    # SM4 独立 crate（实现 cipher::BlockCipher）
+]
+
+[workspace.dependencies]
+digest    = { version = "0.11.1", default-features = false }
+cipher    = { version = "0.5.1",  default-features = false }
+subtle    = { version = "2.6",    default-features = false }
+zeroize   = { version = "1.8",    default-features = false, features = ["derive"] }
+signature = { version = "2.2",    default-features = false }
+hex-literal = "0.4"
+
+# ── libsmx Package 配置（保留现有不变）────────────────────────────────────
 [package]
 name = "libsmx"
 version = "0.3.0"
@@ -52,6 +71,7 @@ hex       = "0.4"
 criterion = { version = "0.5", features = ["html_reports"] }
 rand      = "0.8"
 sm9_core = "0.5.0"
+proptest  = { version = "1", default-features = false, features = ["alloc"] }
 # rustls-provider 集成测试依赖（通过 feature 条件编译保护）
 rustls    = { git = "https://github.com/rustls/rustls.git", branch = "main", default-features = false, features = ["log", "webpki"] }
 pki-types = { package = "rustls-pki-types", version = "1", features = ["alloc"] }