PR Checklist

• Functionality has been tested, no obvious bugs
• Code style follows project conventions
• Documentation/comments updated (if applicable)

Brief Description of Changes

Adds a DisableAutoUpdateCheck setting to skip the automatic update check that runs every 30 days at startup. Users with slow networks can now disable this while retaining manual update checks.

• App.xaml.cs: Early return in CheckUpdate() when setting is enabled
• TrayIconManager.cs: New toggle menu item with checkbox state
• Translations.config: Added Icon_DisableAutoUpdateCheck translation key (English)

private void CheckUpdate()
{
    if (SettingHelper.Get("DisableAutoUpdateCheck", false))
        return;
    // ... existing logic
}

Related Issue (if any)

Fixes #1736

Additional Notes

Manual "Check for Updates..." menu option remains functional regardless of this setting.

• Fixes How to disable QL to check update #1801

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