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/search.json

@@ -0,0 +1,10 @@
+{
+  "label": "Поиск",
+  "placeholder": "Художники, картины, направления…",
+  "resultsLabel": "Результаты поиска",
+  "noMatches": "Ничего не найдено.",
+  "groupArtist": "Художники",
+  "groupMovement": "Направления",
+  "groupPainting": "Картины",
+  "searchFailed": "Ошибка поиска"
+}