* 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
- Add support for custom OAuth providers, including creation, retrieval, updating, and deletion.
- Introduce new model and controller for managing custom OAuth providers.
- Enhance existing OAuth logic to accommodate custom providers.
- Update API routes for custom OAuth provider management.
- Include i18n support for custom OAuth-related messages.
- Introduce Provider interface pattern for standard OAuth protocols
- Create unified controller/oauth.go with common OAuth logic
- Add OAuthError type for translatable error messages
- Add i18n keys and translations (zh/en) for OAuth messages
- Use common.ApiErrorI18n/ApiSuccessI18n for consistent responses
- Preserve backward compatibility for existing routes and data
- Change default language fallback to English instead of Chinese
- Add ErrRedeemFailed typed error for model layer translation
- Migrate remaining hardcoded messages in controller/user.go
- Add translation keys: redeem.failed, user.create_default_token_error, common.uuid_duplicate, common.invalid_input
- 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
