feat(gallery): grid title, subtle download icon, full i18n

- Render block.title as <h3> above the grid when set; the carousel
  variant is unchanged.
- Download CTA in the modal shrunk to a 9×9 icon-only button with
  text-white/80 hover-tint instead of the dark green link colour the
  app's `main a` rule was forcing in. Adds `no-underline` so the
  global underline doesn't sneak back in.
- All previously hardcoded German strings (Download, Schließen,
  modal aria, open aria) now go through translations.ts → CMS
  translation_bundle. Cms_content app.json5 ships the matching keys.

Open follow-up: per-image title/alt/caption is empty on the existing
windwiderstand mediathek gallery → editor needs to fill those if
hover labels are wanted.

src/lib/components/blocks/ImageGalleryBlock.svelte

@@ -167,6 +167,9 @@
   {#if withUrl.length === 0}
     <p class="text-sm text-stein-500">{t(T.image_gallery_empty)}</p>
   {:else if block.variant === "grid"}
+    {#if block.title}
+      <h3 class="text-lg font-semibold text-stein-900 mb-3">{block.title}</h3>
+    {/if}
     <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)}
@@ -175,7 +178,7 @@
             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}`}
+            aria-label={label || t(T.image_gallery_open_aria)}
           >
             <RustyImage
               src={item.url}
@@ -207,7 +210,7 @@
         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"}
+        aria-label={curLabel || t(T.image_gallery_modal_aria)}
         onclick={closeModal}
         transition:fade={{ duration: 150 }}
       >
@@ -216,7 +219,6 @@
           onclick={(e) => e.stopPropagation()}
           role="presentation"
         >
-          <!-- eslint-disable-next-line @typescript-eslint/no-unused-expressions -->
           <img
             src={cur.url}
             alt={curLabel}
@@ -235,10 +237,11 @@
             <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"
+              class="no-underline inline-flex h-9 w-9 items-center justify-center rounded-full text-white/80 hover:text-white hover:bg-white/10 focus:outline-none focus:ring-2 focus:ring-white/40"
+              title={t(T.image_gallery_download)}
+              aria-label={t(T.image_gallery_download)}
             >
-              <Icon icon="mdi:download-outline" class="text-base" aria-hidden="true" />
-              Download
+              <Icon icon="mdi:download-outline" class="text-xl" aria-hidden="true" />
             </a>
           </div>
           {#if withUrl.length > 1}
@@ -263,7 +266,7 @@
             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"
+            aria-label={t(T.image_gallery_close)}
           >
             <Icon icon="mdi:close" class="text-lg" aria-hidden="true" />
           </button>