fix: i18n gaps in popular searches and compare table

- SearchFacade.popularSearches hardcoded English titles regardless of
  active locale. Converted to a getter using translate.t() for the
  displayed title/text; the underlying search query stays the stable
  English canonical term the backend index matches against.
- Compare table and compare page rendered product.name raw instead of
  through getTranslatedField(), same pattern used everywhere else
  product titles are shown (catalog, product detail).
- SearchTrendingService.loadTrending() is a genuine backend gap (no
  trending-search endpoint exists) - already degrades gracefully,
  documented as a gap in BACKEND-API-REFERENCE.md \u00a712.6 rather than
  faked client-side.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/translations.ts

@@ -142,6 +142,10 @@ export interface Translations {
     noResultsHint: string;
     emptyResultsAria: string;
     popularCategories: string;
+    popularSmartphones: string;
+    popularSneakers: string;
+    popularHeadphones: string;
+    popularLaptops: string;
     recommendedProducts: string;
     aiSuggestionHint: string;
     suggestionType: {