feat: implement launch at startup functionality in zn-ai

- Added a new setting for "launch at startup" in the GeneralSettingsPanel.
- Integrated the setting with the existing settings store and IPC mechanisms.
- Implemented platform-specific logic for enabling/disabling startup behavior in the main process.
- Created a new service for managing launch at startup settings, including Linux desktop entry creation.
- Added unit tests for the new functionality and ensured existing tests are updated accordingly.
- Updated i18n messages for the new setting in English, Chinese, and Japanese.

runtime-shared/lib/constants.ts

@@ -81,6 +81,7 @@ export enum CONFIG_KEYS {
   LANGUAGE = 'language',
   FONT_SIZE = 'fontSize',
   MINIMIZE_TO_TRAY = 'minimizeToTray',
+  LAUNCH_AT_STARTUP = 'launchAtStartup',
   PROVIDER = 'provider',
   DEFAULT_MODEL = 'defaultModel',
   AUTO_CHECK_UPDATE = 'autoCheckUpdate',