feat(gallery): grid variant with hover labels + download modal

ImageGalleryBlock now branches on `block.variant`:

- "standard" (default) → existing carousel.
- "grid" → 2/3/4-column thumbnail grid (1:1 squares, w=400/q=75
  through /cms-images). Each tile scales 5% on hover and surfaces
  the image's title/alt/caption/description as a gradient overlay
  caption that fades in on hover and keyboard focus.

Click any tile → fullscreen lightbox (z-100 overlay + 90vh image).
The lightbox carries:
- A download button using the asset's filename (extracted from the
  src URL).
- Prev/Next arrows when there's more than one image (keyboard:
  ←/→), Esc to close, click on the backdrop closes too.
- Position counter (n/total) when applicable.

Type updates in block-types.ts: ImageGalleryBlockData gains
`variant?: "standard"|"grid"` and `title?`. ImageGalleryImage gains
`alt`/`caption`/`title` so the schema's `image` field shape is
honoured for the hover label.

src/lib/block-types.ts

@@ -104,6 +104,10 @@ export interface ImageGalleryImage {
   _slug?: string;
   src?: string;
   description?: string;
+  /** Optionaler Hover-Titel (image-Type: alt/caption/title). */
+  alt?: string;
+  caption?: string;
+  title?: string;
   file?: { url?: string };
   /** Nach resolveContentImages: Proxy-URL zum transformierten Bild (16:9). */
   resolvedSrc?: string;
@@ -115,6 +119,10 @@ export interface ImageGalleryBlockData {
   _slug?: string;
   /** Optionaler Einleitungstext (Markdown). */
   description?: string;
+  /** Optional: oberhalb des Galerie-Modals als Header. */
+  title?: string;
+  /** "standard" = Carousel (Default), "grid" = Thumbnail-Grid mit Modal. */
+  variant?: "standard" | "grid";
   images?: ImageGalleryImage[];
   layout?: BlockLayout;
 }

src/lib/components/blocks/ImageGalleryBlock.svelte

@@ -13,6 +13,22 @@
   const t = useTranslate();
   let { block }: { block: ImageGalleryBlockData } = $props();
 
+  /** Hover-Label aus image-Field — title|alt|caption|description, in dieser Reihenfolge. */
+  function imageLabel(img: ImageGalleryImage): string {
+    return (img.title ?? img.alt ?? img.caption ?? img.description ?? "").trim();
+  }
+
+  /** Dateiname für Download aus Asset-URL ableiten. */
+  function downloadFilename(url: string): string {
+    try {
+      const u = new URL(url);
+      const last = u.pathname.split("/").filter(Boolean).pop();
+      return last ? decodeURIComponent(last) : "image";
+    } catch {
+      return "image";
+    }
+  }
+
   marked.setOptions({ gfm: true });
 
   const layoutClasses = $derived(getBlockLayoutClasses(block.layout));
@@ -45,6 +61,36 @@
 
   let currentIndex = $state(0);
 
+  // Grid-Modal-State: -1 = closed, 0..n-1 = open at index.
+  let modalIndex = $state<number>(-1);
+  const modalOpen = $derived(modalIndex >= 0);
+
+  function openModal(i: number) {
+    modalIndex = i;
+  }
+  function closeModal() {
+    modalIndex = -1;
+  }
+  function modalPrev() {
+    if (modalIndex < 0) return;
+    modalIndex = (modalIndex - 1 + withUrl.length) % withUrl.length;
+  }
+  function modalNext() {
+    if (modalIndex < 0) return;
+    modalIndex = (modalIndex + 1) % withUrl.length;
+  }
+  function onModalKey(e: KeyboardEvent) {
+    if (!modalOpen) return;
+    if (e.key === "Escape") {
+      e.preventDefault();
+      closeModal();
+    } else if (e.key === "ArrowLeft") {
+      modalPrev();
+    } else if (e.key === "ArrowRight") {
+      modalNext();
+    }
+  }
+
   function prev() {
     currentIndex = (currentIndex - 1 + withUrl.length) % withUrl.length;
   }
@@ -109,6 +155,8 @@
   }
 </script>
 
+<svelte:window onkeydown={onModalKey} />
+
 <div class={layoutClasses} data-block-type="image_gallery" data-block-slug={block._slug}>
   {#if descriptionHtml}
     <div class="markdown max-w-none prose prose-zinc mb-4">
@@ -118,6 +166,110 @@
 
   {#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">
+      {#each withUrl as item, i}
+        {@const label = imageLabel(item.img)}
+        <li class="m-0 p-0">
+          <button
+            type="button"
+            class="group relative block w-full aspect-square overflow-hidden rounded-sm bg-stein-100 cursor-zoom-in focus:outline-none focus:ring-2 focus:ring-wald-500"
+            onclick={() => openModal(i)}
+            aria-label={label || `Bild ${i + 1}`}
+          >
+            <RustyImage
+              src={item.url}
+              focal={item.focal}
+              width={400}
+              aspect="1/1"
+              fit="cover"
+              quality={75}
+              alt={label}
+              class="w-full h-full object-cover transition-transform duration-300 group-hover:scale-105"
+              loading={i < 4 ? "eager" : "lazy"}
+            />
+            {#if label}
+              <span
+                class="absolute inset-x-0 bottom-0 px-2 py-1.5 text-xs text-white bg-gradient-to-t from-black/70 via-black/40 to-transparent opacity-0 transition-opacity duration-200 group-hover:opacity-100 group-focus:opacity-100 line-clamp-2"
+              >
+                {label}
+              </span>
+            {/if}
+          </button>
+        </li>
+      {/each}
+    </ul>
+
+    {#if modalOpen}
+      {@const cur = withUrl[modalIndex]}
+      {@const curLabel = imageLabel(cur.img)}
+      <div
+        class="fixed inset-0 z-[100] flex items-center justify-center bg-black/85 p-4"
+        role="dialog"
+        aria-modal="true"
+        aria-label={curLabel || "Bild-Vorschau"}
+        onclick={closeModal}
+        transition:fade={{ duration: 150 }}
+      >
+        <div
+          class="relative max-h-[90vh] max-w-[95vw] flex flex-col items-center gap-3"
+          onclick={(e) => e.stopPropagation()}
+          role="presentation"
+        >
+          <!-- eslint-disable-next-line @typescript-eslint/no-unused-expressions -->
+          <img
+            src={cur.url}
+            alt={curLabel}
+            class="max-h-[80vh] max-w-full rounded-sm bg-stein-900 object-contain shadow-2xl"
+            loading="eager"
+          />
+          <div class="flex w-full items-center justify-between gap-3 text-white">
+            <div class="min-w-0 flex-1">
+              {#if curLabel}
+                <p class="truncate text-sm font-medium">{curLabel}</p>
+              {/if}
+              {#if withUrl.length > 1}
+                <p class="text-xs text-white/60">{modalIndex + 1} / {withUrl.length}</p>
+              {/if}
+            </div>
+            <a
+              href={cur.url}
+              download={downloadFilename(cur.url)}
+              class="inline-flex items-center gap-1.5 rounded-md bg-white/10 px-3 py-1.5 text-sm font-medium text-white hover:bg-white/20 focus:outline-none focus:ring-2 focus:ring-white/50"
+            >
+              <Icon icon="mdi:download-outline" class="text-base" aria-hidden="true" />
+              Download
+            </a>
+          </div>
+          {#if withUrl.length > 1}
+            <button
+              type="button"
+              class="absolute left-2 top-1/2 -translate-y-1/2 inline-flex h-9 w-9 items-center justify-center rounded-full bg-black/50 text-white hover:bg-black/70 focus:outline-none focus:ring-2 focus:ring-white/50"
+              onclick={modalPrev}
+              aria-label={t(T.image_gallery_prev_aria)}
+            >
+              <Icon icon="mdi:chevron-left" class="text-2xl" aria-hidden="true" />
+            </button>
+            <button
+              type="button"
+              class="absolute right-2 top-1/2 -translate-y-1/2 inline-flex h-9 w-9 items-center justify-center rounded-full bg-black/50 text-white hover:bg-black/70 focus:outline-none focus:ring-2 focus:ring-white/50"
+              onclick={modalNext}
+              aria-label={t(T.image_gallery_next_aria)}
+            >
+              <Icon icon="mdi:chevron-right" class="text-2xl" aria-hidden="true" />
+            </button>
+          {/if}
+          <button
+            type="button"
+            class="absolute -top-2 -right-2 inline-flex h-8 w-8 items-center justify-center rounded-full bg-white text-stein-900 shadow-md hover:bg-stein-100 focus:outline-none focus:ring-2 focus:ring-white/50"
+            onclick={closeModal}
+            aria-label="Schließen"
+          >
+            <Icon icon="mdi:close" class="text-lg" aria-hidden="true" />
+          </button>
+        </div>
+      </div>
+    {/if}
   {:else if withUrl.length === 1}
     <figure class="m-0">
       <RustyImage