Add about/contact/installments pages, fix category slot bugs, wire live branding

- Enlarge category carousel thumbnails (90px -> 104-140px responsive) and
  confirm the slider/categories/banner static-image slots are all reading
  correctly from the CMS (verified live, not a wiring bug)
- Fix installments page dropping "هندزفری و هدفون": it's a level-3 category,
  not level-2, so level2.find() silently missed it - use findNode() over the
  whole tree instead
- Extend gen-category-placeholders.mjs to generate a placeholder for every
  category at every level (was level-2 only), needed for the fix above
- Add /about, /contact, /installments pages
  - About: real copy transcribed from the live moalem.shop theme, real
    product photos from the API, text-only brand strip (no scraped logos)
  - Contact: ContactForm.tsx posts to the real POST /contact-submissions,
    branch cards with key-less Google Maps embeds
  - Installments: flat brand-colored hero (no photo/gradient), category
    highlights reusing the same categories slot images as the homepage
- Replace the placeholder header/footer phone number with the real one, add
  real branch addresses and Instagram/Telegram links (src/data/site.ts),
  pulled from the live theme's footer
- Wire logo/favicon to GET /website/favicon (getFavicon() in api.ts) instead
  of the static bundled files, so a dashboard upload now shows automatically;
  layout.tsx metadata is now generateMetadata() to support this. The tenant's
  uploaded logo/favicon currently belongs to a different business - the
  wiring is correct and will self-correct once that's fixed in the dashboard

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

src/components/CategoryCarousel.tsx

@@ -31,12 +31,12 @@ export default function CategoryCarousel({
         modules={[FreeMode]}
         dir="rtl"
         freeMode
-        slidesPerView={3.5}
+        slidesPerView={2.8}
         spaceBetween={12}
         breakpoints={{
-          480: { slidesPerView: 4.5 },
-          768: { slidesPerView: 6.5 },
-          1024: { slidesPerView: 9 },
+          480: { slidesPerView: 3.6 },
+          768: { slidesPerView: 5 },
+          1024: { slidesPerView: 7 },
         }}
       >
         {categories.map((cat, i) => {
@@ -45,10 +45,10 @@ export default function CategoryCarousel({
           return (
             <SwiperSlide key={cat.id}>
               <Link href={categoryHref(cat.id, cat.nameFa, cat.name)} className="group flex flex-col items-center gap-2">
-                <span className="relative size-[90px] overflow-hidden rounded-full bg-surface transition group-hover:bg-brand-soft">
-                  <Image src={art} alt={label} fill sizes="90px" className="object-contain p-2" />
+                <span className="relative size-[104px] overflow-hidden rounded-full bg-surface transition group-hover:bg-brand-soft sm:size-[124px] lg:size-[140px]">
+                  <Image src={art} alt={label} fill sizes="140px" className="object-contain p-3" />
                 </span>
-                <span className="text-center text-[12.5px] text-ink transition group-hover:text-brand">
+                <span className="text-center text-[13.5px] text-ink transition group-hover:text-brand">
                   {label}
                 </span>
               </Link>