Add Russian i18n with DB translations, locale API, and curator review UI.

UI chrome via react-i18next, catalog text in entity_translations with ru.wikipedia seeding, locale-aware search, and Translations page for publish workflow.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/locales/ru/common.json

@@ -0,0 +1,13 @@
+{
+  "loading": "Загрузка…",
+  "close": "Закрыть",
+  "back": "Назад",
+  "save": "Сохранить",
+  "cancel": "Отмена",
+  "yes": "Да",
+  "no": "Нет",
+  "error": "Что-то пошло не так",
+  "localeEn": "EN",
+  "localeRu": "RU",
+  "language": "Язык"
+}