Add mobile swipe gallery, shared ProductCard, dynamic Datenschutz address, GSC verification

- ProductGallery: touch swipe (left/right) now navigates slides on mobile,
  previously click-only.
- New shared ProductCard component used by ProductGrid/RelatedProducts/
  MerklisteGrid — product title is now the card's link (replaces the
  separate "Mehr erfahren" line), consistent aspect ratio across all
  three grids, more compact cards.
- Datenschutz: name/address/email now come from company-settings via a
  new VerantwortlicherBlock, same single-source pattern as Impressum's
  AnbieterAngaben — no more hand-typed address to keep in sync.
- layout.tsx: render googleSearchConsoleVerification via Next's native
  verification.google metadata field.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/layout.tsx

@@ -56,6 +56,9 @@ export async function generateMetadata(): Promise<Metadata> {
       card: "summary_large_image",
       images: seo.defaultOgImage ? [seo.defaultOgImage] : undefined,
     },
+    verification: seo.googleSearchConsoleVerification
+      ? { google: seo.googleSearchConsoleVerification }
+      : undefined,
   };
 }