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/lib.rs

@@ -1,5 +1,6 @@
 mod app_config;
 mod app_store;
+mod auto_launch;
 mod claude_mcp;
 mod claude_plugin;
 mod codex_config;
@@ -559,6 +560,30 @@ pub fn run() {
 
             // 启动阶段不再无条件保存,避免意外覆盖用户配置。
 
+            // 同步开机自启状态：以 settings.json 为准，保持系统项一致
+            {
+                let settings = crate::settings::get_settings();
+                let system_enabled = crate::auto_launch::is_auto_launch_enabled().unwrap_or(false);
+
+                if settings.launch_on_startup != system_enabled {
+                    log::info!(
+                        "开机自启状态不一致：settings={}, system={}，以 settings 为准",
+                        settings.launch_on_startup,
+                        system_enabled
+                    );
+
+                    let sync_result = if settings.launch_on_startup {
+                        crate::auto_launch::enable_auto_launch()
+                    } else {
+                        crate::auto_launch::disable_auto_launch()
+                    };
+
+                    if let Err(e) = sync_result {
+                        log::warn!("同步开机自启状态失败: {}", e);
+                    }
+                }
+            }
+
             // 注册 deep-link URL 处理器（使用正确的 DeepLinkExt API）
             log::info!("=== Registering deep-link URL handler ===");
 
@@ -653,6 +678,8 @@ pub fn run() {
             commands::get_settings,
             commands::save_settings,
             commands::restart_app,
+            commands::set_auto_launch,
+            commands::get_auto_launch_status,
             commands::check_for_updates,
             commands::is_portable_mode,
             commands::get_claude_plugin_status,