feat(quote-carousel): add QuoteCarouselBlock component and related types

- Introduced a new QuoteCarouselBlock component for displaying rotating quotes.
- Added QuoteCarouselBlockData interface to define the structure of the quote carousel data.
- Updated existing components and types to integrate the new quote carousel functionality.
- Enhanced blog-utils to support filtering posts by tags more effectively.
- Made various UI improvements in the Footer and PostCard components for better user experience.

src/lib/components/PostCard.svelte

@@ -33,11 +33,21 @@
 
   const eventDate = $derived(p.isEvent && p.eventDate ? p.eventDate : null);
   const locationText = $derived(p.eventLocation?.text ?? null);
+
+  const tagSlugs = $derived(
+    (post.postTag ?? []).map((t) =>
+      typeof t === "string" ? t : ((t as { _slug?: string })?._slug ?? ""),
+    ),
+  );
+  const hasTerminTag = $derived(tagSlugs.includes("tag-termin"));
+  const isPastEvent = $derived(
+    hasTerminTag && !!p.eventDate && new Date(p.eventDate).getTime() < Date.now(),
+  );
 </script>
 
 <a
   href={href}
-  class="transition-all flex flex-col text-slate-950 no-underline overflow-hidden border border-gray-200 bg-white"
+  class="transition-all flex flex-col text-slate-950 no-underline overflow-hidden border border-gray-200 bg-white relative {isPastEvent ? 'opacity-70 grayscale' : ''}"
 >
   <div class="relative aspect-3/2 w-full overflow-hidden bg-gray-100">
     {#if rawImg}
@@ -70,6 +80,13 @@
         <EventBadges {eventDate} {locationText} />
       </div>
     {/if}
+    {#if isPastEvent}
+      <div class="absolute top-2 right-2">
+        <span class="inline-flex items-center gap-1 rounded-full bg-neutral-800/90 px-2.5 py-1 text-[.65rem] font-semibold uppercase tracking-wide text-white shadow-sm">
+          Vergangen
+        </span>
+      </div>
+    {/if}
   </div>
   <div class="flex-1 flex flex-col justify-start p-4">
     <PostMeta