- New Language row in the main Settings list with current-language summary
- New SettingsLanguage drill-down page with an OutlinedButton + DropdownMenu
picker (scales to any number of languages; same pattern as theme presets)
- Shared supportedLanguages()/languageLabel() helpers — adding a language
is now one entry in one place
- Removed the 4-option segmented pill row from the Appearance page
- Added settings_sec_language string (en + zh)
Co-authored-by: M57 <hy4ri@users.noreply.github.com>