fix: manifest-aware layout picker, real carousel items-per-page, hero arrows/swipe/2-panel

Sprint E: homepage section editor now filters the layout-strategy picker
to each widget's widget-manifest.json supportedLayouts instead of always
showing all 5 strategies. columns field gated to widgets that read it
(hero, product-collection carousel).

Sprint F: closes client bug report (no items-per-page control, hero
carousel not manually/automatically scrollable, no 1-2 slide big-carousel
option). Product carousel item width now driven by layout.columns
(reused, was already editable but dead). Hero widget gains prev/next
arrows, touch swipe, and 1-2 panel mode via the same field.

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

src/app/i18n/ru.ts

@@ -1116,6 +1116,8 @@ export const ru: Translations = {
     slidesLabel: 'Слайды',
     previousProducts: 'Предыдущие товары',
     nextProducts: 'Следующие товары',
+    previousSlide: 'Предыдущий слайд',
+    nextSlide: 'Следующий слайд',
     closeDialog: 'Закрыть диалог',
     dismiss: 'Скрыть',
     qrCode: 'QR-код',