feat: add preistraeger placeholder image and related database migrations

- Introduced a new SVG placeholder image for preistraeger without an image.
- Created migration scripts to add download zip and gallery features to the preistraeger table.
- Added site settings for preistraeger placeholder image in the database.
- Implemented a utility function to retrieve the preistraeger placeholder image URL in the SPA.

src/spa/pages/Preistraeger.tsx

@@ -7,6 +7,7 @@ import { docImageUrl, mediaAlt, mediaUrl } from '@/spa/cmsMediaField';
 import { useIsMobile } from '@/spa/hooks/useIsMobile';
 import Image from '@/spa/components/ui/UnoptimizedImage'
 import { preistraegerIndexContent } from '@/spa/preistraegerIndexContent';
+import { usePreistraegerPlaceholderImage } from '@/spa/preistraegerPlaceholder';
 
 const FF = '"IBM Plex Sans", sans-serif';
 const NAVY = '#111D55';
@@ -25,7 +26,7 @@ const fallbackText = (value: unknown, fallback: string) => typeof value === 'str
 
 const normalizeWinner = (
   doc: CmsRouteDoc,
-  fallbackImage: string,
+  placeholderImage: string,
   fallbackWinner: typeof preistraegerIndexContent.card.fallbackWinner,
 ): Winner => ({
   id: String(doc.id),
@@ -34,7 +35,7 @@ const normalizeWinner = (
   category: String(doc.category || fallbackWinner.category || preistraegerIndexContent.card.fallbackWinner.category),
   year: Number(doc.year || new Date().getFullYear()),
   type: String(doc.awardType || fallbackWinner.awardType || preistraegerIndexContent.card.fallbackWinner.awardType),
-  img: docImageUrl(doc, fallbackImage),
+  img: docImageUrl(doc, placeholderImage),
   shortDesc: String(doc.shortDesc || doc.description || doc.meta?.description || ''),
   longDesc: String(doc.longDesc || doc.description || doc.meta?.description || ''),
   quote: String(doc.quote || ''),
@@ -48,6 +49,7 @@ const normalizeWinner = (
 
 export default function Preistraeger() {
   const isMobile = useIsMobile();
+  const placeholderImage = usePreistraegerPlaceholderImage();
   const cms = (useCmsRoute()?.doc?.preistraegerIndex || {}) as PreistraegerIndexCms;
   const cmsPreistraeger = useCmsCollection('preistraeger');
   const hero = { ...preistraegerIndexContent.hero, ...(cms.hero || {}) };
@@ -56,15 +58,11 @@ export default function Preistraeger() {
   const empty = { ...preistraegerIndexContent.empty, ...(cms.empty || {}) };
   const card = useMemo(() => ({ ...preistraegerIndexContent.card, ...(cms.card || {}) }), [cms.card]);
   const cta = { ...preistraegerIndexContent.cta, ...(cms.cta || {}) };
-  const cardFallbackImage = useMemo(
-    () => mediaUrl(card.fallbackImage, `/images/${preistraegerIndexContent.card.fallbackImageFilename}`),
-    [card],
-  );
   const winners = useMemo(() => {
     const fallbackWinner = card.fallbackWinner || preistraegerIndexContent.card.fallbackWinner;
-    if (cmsPreistraeger.length) return cmsPreistraeger.map((doc) => normalizeWinner(doc, cardFallbackImage, fallbackWinner)).filter((winner) => winner.slug);
+    if (cmsPreistraeger.length) return cmsPreistraeger.map((doc) => normalizeWinner(doc, placeholderImage, fallbackWinner)).filter((winner) => winner.slug);
     return WINNERS;
-  }, [card, cardFallbackImage, cmsPreistraeger]);
+  }, [card, cmsPreistraeger, placeholderImage]);
   const years = useMemo(() => [...new Set(winners.map((winner) => winner.year))].sort((a, b) => b - a), [winners]);
   const [activeYear, setActiveYear] = useState<number | undefined>(undefined);
   const selectedYear = activeYear ?? years[0] ?? new Date().getFullYear();