* build: add nlohmann/json library
* build(deps): add harfbuzz dependency
* feat(cmake): add guard to reject macOS builds
* feat(font): add HarfBuzz shaping and replace font with unifont
* feat(localization): add i18n support with en_US and zh_CN translations
Implement Localization class to load JSON translation files. Replace hardcoded strings in UI with translation keys and update sliders/combo buttons to use dynamic text.
* feat(localization): detect system locale for language default
* feat(settings): add language selection option with restart notification
* fix: use vckpg to add freetype on windows
