Redesign category showcase and convert products section to carousel

- Replace icon-based category tiles with curated photo cards (brown
  bottom overlay, single-row layout, taller aspect ratio, tighter gaps,
  no card frame, light brown section background) via new
  CategoryShowcase component and categoryIcons fallback images.
- Add ScrollReveal component for page-enter animations, used across
  the category showcase and other sections.
- Turn the homepage "New Products" grid into a horizontal snap-scroll
  carousel with prev/next controls (ProductsCarousel).
- Extend Pagination and the products page to preserve categoryId
  filters, and widen aspectRatioToCss to accept undefined.
- Document the static-image-slots system and API client conventions
  in CLAUDE.md.

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

.gitignore

@@ -42,3 +42,7 @@ next-env.d.ts
 
 # claude code local settings
 .claude/settings.local.json
+
+# raw source photos (unoptimized originals; only the derived files in
+# public/images/ are actually used by the site)
+/public/Image Sample/