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/en/home.json

@@ -0,0 +1,20 @@
+{
+  "title": "Virtual Art Gallery",
+  "subtitle": "Explore art history on an interactive timeline — enter 3D galleries and discover connections between artists and masterpieces.",
+  "loadingArtHistory": "Loading art history…",
+  "loadingPortraits": "Loading portraits…",
+  "openingArtistGallery": "Opening artist gallery…",
+  "openingMovementGallery": "Opening movement gallery…",
+  "backToTimeline": "← Back to Timeline",
+  "backToGallery": "← Back to Gallery",
+  "curatorLogin": "Curator login",
+  "curatorLogout": "Log out",
+  "signedInAs": "Signed in as {{username}}",
+  "debugMode": "Debug mode",
+  "showMoreDebug": "Show more (debug)",
+  "checkup": "Checkup",
+  "translations": "Translations",
+  "curatorRequiredTitle": "Curator access required",
+  "curatorRequiredBody": "Sign in as a curator to use this tool.",
+  "backToGalleryBtn": "Back to gallery"
+}