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/en.ts

@@ -670,6 +670,18 @@ export const en: Translations = {
     widgetHeightDesc: 'Preferred height for this widget (e.g. "480px" or "60vh").',
     widgetOverlayDesc: 'Show a dark overlay behind hero text for readability.',
     widgetAutoplayDesc: 'Automatically rotate hero slides without shopper interaction.',
+    heroLayoutFullBleed: 'Full width (edge to edge)',
+    heroLayoutBoxed: 'Boxed (within page margins)',
+    heroHeightCompact: 'Compact',
+    heroHeightMedium: 'Medium',
+    heroHeightTall: 'Tall',
+    heroHeightFullScreen: 'Full screen',
+    heroSlides: 'Slides',
+    heroSlidesHint: 'Add more slides to turn this into a slideshow. The fields above are slide 1. Autoplay and dots only appear once you have more than one slide.',
+    heroSlideTitlePlaceholder: 'Slide title',
+    heroSlideSubtitlePlaceholder: 'Slide subtitle',
+    addSlide: 'Add slide',
+    removeSlide: 'Remove slide',
     widgetColumnsDesc: 'Number of category tiles per row.',
     widgetCardsPerRowDesc: 'Number of product cards shown per row.',
     widgetFiltersDesc: 'Show filter controls alongside the product collection.',
@@ -836,6 +848,26 @@ export const en: Translations = {
     widgetRemove: 'Remove',
     widgetRemoveConfirm: 'Remove this section from the homepage?',
     widgetAdvancedSettings: 'Advanced settings',
+    homepageBlocksHint: 'These are the blocks customers see on your homepage, top to bottom. Drag the handle to reorder.',
+    addBlockHint: 'Add a block to your homepage:',
+    dragToReorder: 'Drag to reorder',
+    blockRemoveConfirm: 'Remove this block from the homepage?',
+    blockHero: 'Hero banner',
+    blockHeroDesc: 'The large welcome banner at the top of your homepage, with a title and call-to-action button.',
+    blockCategories: 'Categories',
+    blockCategoriesDesc: 'A grid of category tiles so customers can browse by department.',
+    blockFeaturedProducts: 'Featured products',
+    blockFeaturedProductsDesc: 'A grid of hand-picked or best-selling products.',
+    blockProductCarousel: 'Product carousel',
+    blockProductCarouselDesc: 'A horizontally scrolling row of products, with arrows to browse more.',
+    blockRecentlyViewed: 'Recently viewed',
+    blockRecentlyViewedDesc: 'Shows each customer the products they looked at recently.',
+    blockBanner: 'Promo banner',
+    blockBannerDesc: 'A single image with a headline and button, for sales or announcements.',
+    blockPartners: 'Partner logos',
+    blockPartnersDesc: 'A row of brand or partner logos for trust and credibility.',
+    blockCustomHtml: 'Custom block',
+    blockCustomHtmlDesc: 'Free-form HTML for anything the other blocks do not cover.',
   },
   dashboard: {
     title: 'Dashboard',