feat(builder): visual homepage blocks, merchant-language widget settings, real carousel arrows

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

P0 user feedback: homepage builder showed raw section.id like 'section-hero'/'section-categories'; hero widget exposed 'full-bleed'/'boxed' and raw px/vh as free text with no explanation; Overlay/Autoplay toggles made no sense without a slides concept; product carousel widgets rendered arrows nowhere near a working carousel.

Homepage section (sections list -> visual blocks):
- Replaced raw section.id display with a merchant-facing block catalog (icon + name + one-line explanation) for hero/categories/featured-products/product-carousel/recently-viewed/banner/partners/custom-html
- Added block catalog picker to append new blocks (was fixed at whatever the seed data had - task asked 'what if we add manually? not fixed 3')
- Added duplicate and remove per block, alongside the existing drag-to-reorder
- Verified in browser: labels render correctly, add-block and duplicate both confirmed working end-to-end

Widgets section (hero widget):
- 'Layout' free-text replaced with a select (Full width / Boxed) instead of typing 'full-bleed'/'boxed' blind
- 'Height' free-text replaced with a select (Compact/Medium/Tall/Full screen) mapped to real vh values
- New Slides editor: title/subtitle pairs an admin can add/remove: this is the actual multi-slide data the Overlay/Autoplay toggles were referring to with nothing to point at before
- HeroWidgetData contract gains slides[]/autoplay; HeroWidgetComponent now renders a real rotator (dots, click-to-jump, autoplay interval) when more than one slide exists - previously autoplay/overlay props existed but there was no slideshow behavior anywhere to control

Carousel arrows root cause and fix:
- widget-manifest.json offers 'carousel' as a layout option for product-collection/product-carousel widgets, and the admin UI let you select it, but ProductCarouselWidgetComponent always rendered a static CSS grid regardless - there was no carousel implementation to have arrows in the first place
- Now renders a real horizontally-scrollable strip with working prev/next buttons (native scrollBy, disabled at each end) when section.layout.strategy === 'carousel'; falls back to the existing grid otherwise
- Confirmed src/app/components/items-carousel (a PrimeNG p-carousel) is dead code, not wired into any route or widget - not the source of the reported bug

New builder.* i18n keys (en/ru/hy), zero duplicate-key collisions verified via scan

src/app/i18n/translations.ts

@@ -668,6 +668,18 @@ export interface Translations {
     widgetHeightDesc: string;
     widgetOverlayDesc: string;
     widgetAutoplayDesc: string;
+    heroLayoutFullBleed: string;
+    heroLayoutBoxed: string;
+    heroHeightCompact: string;
+    heroHeightMedium: string;
+    heroHeightTall: string;
+    heroHeightFullScreen: string;
+    heroSlides: string;
+    heroSlidesHint: string;
+    heroSlideTitlePlaceholder: string;
+    heroSlideSubtitlePlaceholder: string;
+    addSlide: string;
+    removeSlide: string;
     widgetColumnsDesc: string;
     widgetCardsPerRowDesc: string;
     widgetFiltersDesc: string;
@@ -835,6 +847,26 @@ export interface Translations {
     widgetRemove: string;
     widgetRemoveConfirm: string;
     widgetAdvancedSettings: string;
+    homepageBlocksHint: string;
+    addBlockHint: string;
+    dragToReorder: string;
+    blockRemoveConfirm: string;
+    blockHero: string;
+    blockHeroDesc: string;
+    blockCategories: string;
+    blockCategoriesDesc: string;
+    blockFeaturedProducts: string;
+    blockFeaturedProductsDesc: string;
+    blockProductCarousel: string;
+    blockProductCarouselDesc: string;
+    blockRecentlyViewed: string;
+    blockRecentlyViewedDesc: string;
+    blockBanner: string;
+    blockBannerDesc: string;
+    blockPartners: string;
+    blockPartnersDesc: string;
+    blockCustomHtml: string;
+    blockCustomHtmlDesc: string;
   };
   dashboard: {
     title: string;