feat(blocks): data-block PascalCase identifier on every CMS block

Adds data-block="PascalName" alongside existing data-block-type
snake_case so blocks can be located via [data-block="Calendar"] etc.
in DevTools. Snake-case attribute kept for backward compat.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/components/blocks/LinkListBlock.svelte

@@ -28,7 +28,7 @@
   );
 </script>
 
-<div class="link-list {layoutClasses}" data-block-type="link_list" data-block-slug={block._slug}>
+<div class="link-list {layoutClasses}" data-block="LinkList" data-block-type="link_list" data-block-slug={block._slug}>
   {#if block.headline}
     <h3 class="mb-3 text-sm font-semibold tracking-wide uppercase">{block.headline}</h3>
   {/if}