新增: Tauri 2.0 桌面版脚手架(B0)

- src-tauri/ 完整项目结构: Cargo.toml / build.rs / tauri.conf.json
- Rust 入口 lib.rs: ping IPC 命令验证双向通信
- 应用图标生成(SVG → ico/icns/png 多尺寸)
- Tauri 窗口配置: 1280×800, 最小 900×600, 可缩放
- package.json 新增 tauri / tauri:dev / tauri:build 脚本
- vite.config.ts 环境检测: Tauri 模式端口 5173, Web 模式 8080
- @tauri-apps/cli + @tauri-apps/api 依赖安装
- cargo check 编译通过,前端构建不受影响
- 桌面版与 Web 版共享同一套前端代码

src-tauri/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "u-ppt"
+version = "1.0.0"
+description = "在线演示工具 - 桌面版"
+authors = ["u-ppt"]
+edition = "2021"
+rust-version = "1.77"
+
+[lib]
+name = "u_ppt_lib"
+crate-type = ["staticlib", "cdylib", "rlib"]
+
+[build-dependencies]
+tauri-build = { version = "2", features = [] }
+
+[dependencies]
+tauri = { version = "2", features = [] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"