feat(image): enhance image handling with new properties and responsive support

- Updated PostEntry type to include _rawImageUrl and _imageFocal for improved image management.
- Refactored image handling in various components to utilize the new properties, ensuring better focal point support and responsive image rendering.
- Introduced warmResponsiveImage function for pre-fetching image variants to optimize loading performance.
- Replaced CmsImage component with RustyImage in multiple blocks for consistent image processing.

src/lib/rusty-image.server.ts

@@ -143,7 +143,7 @@ export interface ResponsiveImageOptions {
 }
 
 const DEFAULT_WIDTHS = [640, 960, 1280, 1600, 1920, 2400];
-const DEFAULT_FORMATS: Array<'avif' | 'webp' | 'jpeg'> = ['avif', 'webp', 'jpeg'];
+const DEFAULT_FORMATS: Array<'avif' | 'webp' | 'jpeg'> = ['webp', 'jpeg'];
 const MIME_FOR_FORMAT: Record<'avif' | 'webp' | 'jpeg', string> = {
   avif: 'image/avif',
   webp: 'image/webp',
@@ -232,3 +232,26 @@ export async function buildResponsiveImage(
     ...(lqip ? { lqip } : {}),
   };
 }
+
+/**
+ * Fire-and-forget Cache-Warmup: alle srcset-Varianten + Fallback parallel anrequesten.
+ * Nutzt SvelteKit's `event.fetch` für Self-Calls (keine echten HTTP-Roundtrips in Prod-SSR).
+ * Blockiert den Response NICHT — läuft im Hintergrund weiter.
+ */
+export function warmResponsiveImage(
+  responsive: ResponsiveImage | null,
+  fetchFn: typeof fetch,
+): void {
+  if (!responsive) return;
+  const urls = new Set<string>();
+  urls.add(responsive.fallback);
+  for (const s of responsive.sources) {
+    for (const entry of s.srcset.split(',')) {
+      const url = entry.trim().split(/\s+/)[0];
+      if (url) urls.add(url);
+    }
+  }
+  for (const u of urls) {
+    void fetchFn(u).catch(() => {});
+  }
+}