Error handlers had a separate Jinja2Templates instance without the _
global function, causing UndefinedError when rendering base.html
(which now calls {{ _(key, current_locale) }}).
- Register _() from translator module as Jinja2 global on error_handlers templates
- Add current_locale to get_template_context() from request.state.locale
Add i18n support to the blog web UI with 4 languages (en/ru/fr/de),
80 translation keys, automatic Accept-Language detection, persistent
locale cookie, and a language switcher dropdown in the header.
- Infrastructure: TranslationService, translation dicts, convenience _()
- Presentation: locale middleware, /web/lang/{locale} switcher route
- Templates: all 9 templates use {{ _(key, current_locale) }}
- Tests: 26 tests across TranslationService, locale detection helpers
- Docs: TEST_MODEL.md and FEATURE_INFRASTRUCTURE.md updated with TC-UNIT-811-821
