fix(gallery): use not-prose on grid <ul> to escape Typography styles

The Tailwind Typography (`prose prose-zinc`) wrapper applied higher in
the page hierarchy injects `.prose ul` rules — list-style: disc, an
indent, and ::marker color — at a higher specificity than single-class
utilities, so list-none/p-0/m-0 silently lost.

`not-prose` is the official escape hatch from the typography plugin
and zaps every prose rule on the element plus its descendants. One
class instead of three \!important overrides.

src/lib/components/blocks/ImageGalleryBlock.svelte

@@ -167,7 +167,7 @@
   {#if withUrl.length === 0}
     <p class="text-sm text-stein-500">{t(T.image_gallery_empty)}</p>
   {:else if block.variant === "grid"}
-    <ul class="grid grid-cols-2 gap-2 sm:grid-cols-3 md:grid-cols-4 list-none p-0 m-0">
+    <ul class="not-prose grid grid-cols-2 gap-2 sm:grid-cols-3 md:grid-cols-4">
       {#each withUrl as item, i}
         {@const label = imageLabel(item.img)}
         <li class="m-0 p-0">