feat: 重写为 Tauri + React + TypeScript (v4.0)

完全移除旧 C+IUP 代码，改用 Tauri 2.x + React 19 + TypeScript + Rust 技术栈重写。
功能与 v3.1 完全等价：

- React 前端：Tailwind CSS 4、Zustand 状态管理、i18next 国际化
- Rust 后端：winreg 注册表读写、Win32 API FFI 调用
- 核心逻辑：StringList、UndoRedoManager、PathManager、Import/Export
- 深色模式、中英文切换、键盘快捷键、合并预览
- 66 个 Vitest 单元测试

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "patheditor"
+version = "4.0.0"
+description = "Windows PATH Environment Variable Editor"
+authors = ["刘航宇"]
+license = "MIT"
+repository = "https://github.com/LHY0125/PathEditor"
+edition = "2021"
+rust-version = "1.77.2"
+
+[lib]
+name = "app_lib"
+crate-type = ["staticlib", "rlib"]
+
+[build-dependencies]
+tauri-build = { version = "2.6.2", features = [] }
+
+[dependencies]
+serde_json = "1.0"
+serde = { version = "1.0", features = ["derive"] }
+log = "0.4"
+tauri = { version = "2.11.2", features = [] }
+tauri-plugin-log = "2"
+tauri-plugin-dialog = "2"
+
+# Windows API
+winreg = "0.52"
+dirs = "5"
+chrono = "0.4"