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>

src/components/ScrollReveal.tsx

@@ -0,0 +1,47 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import type { ReactNode } from "react";
+
+export default function ScrollReveal({
+  children,
+  delay = 0,
+  className = "",
+}: {
+  children: ReactNode;
+  delay?: number;
+  className?: string;
+}) {
+  const ref = useRef<HTMLDivElement>(null);
+  const [visible, setVisible] = useState(false);
+
+  useEffect(() => {
+    const el = ref.current;
+    if (!el) return;
+
+    const observer = new IntersectionObserver(
+      ([entry]) => {
+        if (entry.isIntersecting) {
+          setVisible(true);
+          observer.unobserve(el);
+        }
+      },
+      { threshold: 0.15 }
+    );
+
+    observer.observe(el);
+    return () => observer.disconnect();
+  }, []);
+
+  return (
+    <div
+      ref={ref}
+      style={{ transitionDelay: visible ? `${delay}ms` : "0ms" }}
+      className={`transition-all duration-700 ease-out ${
+        visible ? "opacity-100 translate-y-0" : "opacity-0 translate-y-8"
+      } ${className}`}
+    >
+      {children}
+    </div>
+  );
+}