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>

BACKEND-API-REFERENCE.md

@@ -522,3 +522,13 @@ Separately, `createCartPayment()` (payment-gateway charge creation) still sends
 { "telegramUserId": "8823771" }
 ```
 `telegramUserId` may be `null` for a non-Telegram web session - decide whether to also accept an email address as an alternative identifier (the frontend has no email capture on this flow today, so that would need a small frontend addition too). Once this ships, the frontend's localStorage fallback becomes purely a resilience path rather than the common case, and could optionally sync any locally-queued subscriptions on next successful call.
+
+### 12.6 Trending search terms
+
+**Gap:** `SearchTrendingService.loadTrending()` is a stub returning `of(null)` - no trending-searches endpoint exists. It already degrades gracefully (UI hides the trending section rather than showing an error), so this is purely a missing-feature gap, not a bug.
+
+**Ask:** an endpoint returning the top N search queries over some recent window, e.g.:
+```json
+{ "trending": [{ "query": "wireless earbuds", "count": 214 }, { "query": "winter jacket", "count": 187 }] }
+```
+Once it exists, wire `loadTrending()` to it and map `query` -> `SearchSuggestion.title/text`.