feat: update site URLs and enhance image handling

- Changed site URLs in docker-compose and deployment configurations to remove "www" prefix for consistency.
- Improved image handling by introducing warmPostCardImages function for pre-fetching images in posts and tags.
- Enhanced PostCard component with responsive image sizes for better performance.
- Updated layout to include robots meta tag and JSON-LD structured data for improved SEO.
- Added loading state for images in TopBanner component to enhance user experience.

src/lib/components/TopBanner.svelte

@@ -80,6 +80,19 @@
   const hasPageTitle = $derived((headline != null && headline !== "") || (subheadline != null && subheadline !== ""));
   const showBanner = $derived(hasImage || hasText || hasPageTitle);
   const altText = $derived(banner?.headline ?? headline ?? "");
+
+  let imgEl = $state<HTMLImageElement | null>(null);
+  let imgLoaded = $state(false);
+
+  const currentSrc = $derived(responsive?.fallback ?? resolvedImages[0] ?? "");
+  $effect(() => {
+    // reset on src change, then probe cache
+    void currentSrc;
+    imgLoaded = false;
+    queueMicrotask(() => {
+      if (imgEl?.complete && imgEl.naturalWidth > 0) imgLoaded = true;
+    });
+  });
 </script>
 
 {#if showBanner}
@@ -98,13 +111,17 @@
               <img
                 src={responsive.fallback}
                 alt={altText}
-                class="w-full object-cover max-h-[400px] lg:max-h-[600px] max-w-[1920px] aspect-square sm:aspect-video lg:aspect-24/9 text-transparent"
+                class="w-full object-cover max-h-[400px] lg:max-h-[600px] max-w-[1920px] aspect-square sm:aspect-video lg:aspect-24/9 text-transparent transition-opacity duration-500"
+                class:opacity-0={!imgLoaded}
+                class:opacity-100={imgLoaded}
                 width={responsive.width}
                 height={responsive.height}
                 style={imgStyle}
                 loading="eager"
                 fetchpriority="high"
                 decoding="async"
+                bind:this={imgEl}
+                onload={() => (imgLoaded = true)}
               />
             </picture>
           {/key}
@@ -113,12 +130,15 @@
             <img
               src={resolvedImages[0]}
               alt={altText}
-              class="w-full object-cover max-h-[400px] lg:max-h-[600px] max-w-[1920px] aspect-square sm:aspect-video lg:aspect-24/9 text-transparent"
+              class="w-full object-cover max-h-[400px] lg:max-h-[600px] max-w-[1920px] aspect-square sm:aspect-video lg:aspect-24/9 text-transparent transition-opacity duration-500"
+              class:opacity-0={!imgLoaded}
+              class:opacity-100={imgLoaded}
               width={1920}
               height={600}
               style={imgStyle}
               loading="eager"
               fetchpriority="high"
+              onload={() => (imgLoaded = true)}
             />
           {/key}
         {/if}