Add darkened photo hero to shop page

Deliberately using the low-res thumbnail the client dropped in the repo
(180x280px) so the pixelation is visible live — the treatment itself is
the right direction, it just needs a real high-res source photo. No
customers yet, so safe to ship as a visible placeholder rather than a
mockup.

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

layouts/shop/list.html

@@ -1,5 +1,12 @@
 {{ define "main" }}
-<h1>{{ .Title }}</h1>
+<div class="shop-hero">
+  <img class="shop-hero-img" src="{{ "images/shop-hero.jpg" | relURL }}" alt="">
+  <div class="shop-hero-overlay"></div>
+  <div class="shop-hero-copy">
+    <h1>{{ .Title }}</h1>
+    <p>Small-batch, cold-processed, cured for six weeks &mdash; here's what's ready now.</p>
+  </div>
+</div>
 
 <div class="product-grid">
   {{ range .Site.Data.products }}