- Create Liquid i18n filter (LiquidFilters::I18nFilter) exposing I18n.t() as `t` filter
- Replace hardcoded English strings in all 26 Liquid email templates with i18n keys
- Replace hardcoded English strings in all 4 Devise ERB email templates with t() calls
- Translate all mailer subjects to use I18n.t() for locale-aware rendering
- Add comprehensive pt-BR translations for all transactional emails
- Fix ApplicationRecord#to_drop to walk STI hierarchy (SuperAdmin -> User)