SEO-friendly id-based URLs, sitemap/robots, and homepage category banners

- Replace legacy DB-slug URLs with /products/{id}/{fa-slug},
  /products/category/{id}/{fa-slug}, and /blog/{id}/{fa-slug}, backed by
  the new by-id API endpoints and a Persian slugify helper
- Add /sitemap.xml (index) + /sitemap-main.xml + /sitemap-products.xml
  and /robots.txt pointing to it
- Register the three-banner-row slot in the static-image-slots catalog
- Replace the homepage category carousel with a 3-column linkable
  ThreeBanners section wired to that slot
- Remove the now-superseded root prompt files (moved into Ai data/)

src/components/Footer.tsx

@@ -1,6 +1,7 @@
 import Link from "next/link";
 import Logo from "./Logo";
 import { headerNavLinks, siteInfo } from "@/data/site";
+import { categoryHref } from "@/lib/slug";
 import type { CategoryNode } from "@/lib/types";
 import {
   InstagramIcon,
@@ -66,7 +67,7 @@ export default function Footer({ categoryColumns }: { categoryColumns: CategoryN
           <ul className="space-y-2.5 text-sm">
             {categoryItems.map((cat) => (
               <li key={cat.id}>
-                <Link href={`/products?category=${cat.slug}`} className="hover:text-gold transition-colors">
+                <Link href={categoryHref(cat)} className="hover:text-gold transition-colors">
                   {cat.nameFa}
                 </Link>
               </li>