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/main.tsx

@@ -1,6 +1,7 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
 import './index.css'
+import './i18n'
 import App from './App.tsx'
 import { AuthProvider } from './context/AuthContext.tsx'