Fix cart-mini fragment using internal URL for logo image

site().logo resolves against g.host which is cart:8000 on internal
fragment requests. Use blog_url() for the public blog asset URL.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/fragments/cart_mini.html

@@ -6,7 +6,7 @@
       class="h-full w-full font-bold text-5xl flex-shrink-0 flex flex-row items-center gap-1"
     >
       <img
-        src="{{ site().logo }}"
+        src="{{ blog_url('/static/img/logo.jpg') }}"
         class="h-full w-full rounded-full object-cover border border-stone-300 flex-shrink-0"
       >
     </a>