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>

db/migrate-i18n.sql

@@ -0,0 +1,36 @@
+-- Internationalization: locale-specific catalog text (canonical English stays in main tables).
+
+CREATE TABLE IF NOT EXISTS entity_translations (
+  id SERIAL PRIMARY KEY,
+  entity_type VARCHAR(32) NOT NULL,
+  entity_id INTEGER NOT NULL,
+  locale VARCHAR(10) NOT NULL,
+  field_name VARCHAR(64) NOT NULL,
+  value TEXT NOT NULL,
+  status VARCHAR(20) NOT NULL DEFAULT 'draft',
+  source VARCHAR(120),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  UNIQUE (entity_type, entity_id, locale, field_name)
+);
+
+CREATE INDEX IF NOT EXISTS entity_translations_lookup_idx
+  ON entity_translations (entity_type, entity_id, locale);
+
+CREATE INDEX IF NOT EXISTS entity_translations_locale_field_idx
+  ON entity_translations (locale, field_name);
+
+CREATE INDEX IF NOT EXISTS entity_translations_value_lower_idx
+  ON entity_translations (locale, lower(value));
+
+CREATE OR REPLACE FUNCTION entity_translations_touch_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+  NEW.updated_at = now();
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS entity_translations_updated_at ON entity_translations;
+CREATE TRIGGER entity_translations_updated_at
+  BEFORE UPDATE ON entity_translations
+  FOR EACH ROW EXECUTE PROCEDURE entity_translations_touch_updated_at();