feat: 重构项目结构并添加核心功能

refactor: 将代码按功能模块重新组织到 core/runtime/control 等目录
feat(core): 添加 Context、FlowNode 等核心 trait 和类型
feat(runtime): 实现 FlowEngine 和状态管理
feat(control): 添加顺序/并行/条件控制流节点
feat(nodes): 实现 HTTP/DB/MQ 等业务节点
docs: 更新 README 添加架构说明和快速开始示例
test: 添加性能测试脚本和示例代码

Cargo.lock

@@ -1635,6 +1635,15 @@ version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "650eef8c711430f1a879fdd01d4745a7deea475becfb90269c06775983bbf086"
 
+[[package]]
+name = "no-std-compat"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b93853da6d84c2e3c7d730d6473e8817692dd89be387eb01b94d7f108ecb5b8c"
+dependencies = [
+ "spin",
+]
+
 [[package]]
 name = "nu-ansi-term"
 version = "0.50.3"
@@ -2206,6 +2215,7 @@ dependencies = [
  "ahash",
  "bitflags",
  "instant",
+ "no-std-compat",
  "num-traits",
  "once_cell",
  "rhai_codegen",
@@ -2507,6 +2517,12 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "spin"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
+
 [[package]]
 name = "sptr"
 version = "0.3.2"