* feat(localization): added zh_TW
* fixed based on @coderabbitai
* updated false translation for zh_TW
* new workflow
* revert
* fixed a lot of translations
* turned most zh to zh-CN
* fallbacklang
* bruh
* eliminate ALL _
* fix: paths and other miscs thanks @Calcium-Ion
* fixed translation and temp fix for preferencessettings.js
* fixed translation error
* fixed issue about legacy support
* reverted stupid coderabbit's suggestion
Replace icon-based language options with plain text labels in both the
header dropdown and preferences settings to keep the UI clean and
avoid potential controversies. Remove unused country-flag-icons dependency.
- Add go-i18n library for internationalization
- Create i18n package with translation keys and YAML locale files (zh/en)
- Implement i18n middleware for language detection from user settings and Accept-Language header
- Add Language field to UserSetting DTO
- Update API response helpers with i18n support (ApiErrorI18n, ApiSuccessI18n)
- Migrate hardcoded messages in token, redemption, and user controllers
- Add frontend language preference settings component
- Sync language preference across header selector and user settings
- Auto-restore user language preference on login
