fix:系统文件对话框关闭后，主窗口自动显示

[Flinglin]

在关闭系统文件对话框后，显示主窗口，便于后续操作。例如在添加本地启动后，需要对启动项指定别名。这可能更符合多数用户的使用习惯

[gemini-code-assist]

Code Review

This pull request introduces a centralized openDialog utility in windowUtils.ts to replace direct Electron dialog.showOpenDialog calls across multiple renderer API files, standardizing dialog handling and result processing. Review feedback recommends using BrowserWindow instead of BaseWindow for type consistency and adding a safety check to ensure the parent window is not destroyed before calling show(). A non-null assertion for mainWindow in localShortcuts.ts was also suggested for consistency.