feat(tauri): 摄像头/麦克风权限配置（macOS 授权一次 + Windows 兼容）

- Info.plist：NSCameraUsageDescription / NSMicrophoneUsageDescription（授权一次后不再询问）
- tauri.conf.json：macOSPrivateApi + WebView2 autoplay 允许（自动问候语音不被拦）+ nsis/app/dmg 双平台打包
- Cargo.toml：tauri 启用 macos-private-api feature

src-tauri/Cargo.toml

@@ -13,7 +13,7 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = [] }
+tauri = { version = "2", features = ["macos-private-api"] }
 tauri-plugin-opener = "2"
 tauri-plugin-autostart = "2"
 serde = { version = "1", features = ["derive"] }