feat(settings): add auto-launch on system startup feature

Implement auto-launch functionality with proper state synchronization
and error handling across Windows, macOS, and Linux platforms.

Key changes:
- Add auto_launch module using auto-launch crate 0.5
- Define typed errors (AutoLaunchPathError, AutoLaunchEnableError, etc.)
- Sync system state with settings.json on app startup
- Only call system API when auto-launch state actually changes
- Add UI toggle in Window Settings panel
- Add i18n support for auto-launch settings (en/zh)

Implementation details:
- Settings file (settings.json) is the single source of truth
- On startup, system state is synced to match settings.json
- Error handling uses Rust type system with proper error propagation
- Frontend optimized to avoid unnecessary system API calls

Platform support:
- Windows: HKEY_CURRENT_USER registry modification
- macOS: AppleScript-based launch item (configurable to Launch Agent)
- Linux: XDG autostart desktop file

src-tauri/src/commands/settings.rs

@@ -37,3 +37,20 @@ pub async fn set_app_config_dir_override(
     crate::app_store::set_app_config_dir_to_store(&app, path.as_deref())?;
     Ok(true)
 }
+
+/// 设置开机自启
+#[tauri::command]
+pub async fn set_auto_launch(enabled: bool) -> Result<bool, String> {
+    if enabled {
+        crate::auto_launch::enable_auto_launch().map_err(|e| e.to_string())?;
+    } else {
+        crate::auto_launch::disable_auto_launch().map_err(|e| e.to_string())?;
+    }
+    Ok(true)
+}
+
+/// 获取开机自启状态
+#[tauri::command]
+pub async fn get_auto_launch_status() -> Result<bool, String> {
+    crate::auto_launch::is_auto_launch_enabled().map_err(|e| e.to_string())
+}