Improve social media OG/Twitter meta for posts

- Fix bug: post page was overriding og:image with 150x200 thumbnail
- og:type = "article" for posts (was always "website")
- article:published_time, article:modified_time, article:author, article:tag
- og:image:alt + twitter:image:alt (post headline)
- twitter:label1/data1 with reading time
- Remove thumbnail fallback from socialImage (falls back to site logo instead)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/post/[slug]/+page.server.ts

@@ -303,13 +303,22 @@ export const load: PageServerLoad = async ({ params, locals, url, setHeaders })
     translations,
     seoTitle: post.seoTitle ?? postHeadline,
     seoDescription: postDescription,
-    socialImage: postSocialImageAbs ?? postImageUrl ?? undefined,
+    socialImage: postSocialImageAbs ?? undefined,
+    ogType: 'article' as const,
+    ogImageAlt: postHeadline,
+    articlePublishedTime: postCreated,
+    articleModifiedTime: postUpdated,
+    articleAuthor: postAuthor ?? siteName,
+    articleTags: (() => {
+      const tags = (post as { postTag?: Array<{ name?: string }> }).postTag ?? [];
+      return tags.map((t) => (typeof t === 'string' ? t : (t?.name ?? ''))).filter(Boolean);
+    })(),
+    twitterLabel1: 'Lesezeit',
+    twitterData1: `${readingTimeMinutes} Min.`,
     robots: (post as { seoMetaRobots?: string }).seoMetaRobots ?? undefined,
     keywords: (() => {
       const explicit = ((post as { seoKeywords?: string }).seoKeywords ?? '').trim();
       if (explicit) return explicit;
-      // Fallback: join tag names so published posts without explicit keywords
-      // still ship a meaningful <meta name="keywords">.
       const tags = (post as { postTag?: Array<{ name?: string }> }).postTag ?? [];
       const names = tags
         .map((t) => (typeof t?.name === 'string' ? t.name.trim() : ''))

src/routes/post/[slug]/+page.svelte

@@ -14,15 +14,6 @@
   let { data }: { data: PageData } = $props();
 </script>
 
-<svelte:head>
-  <title>{data.seoTitle}</title>
-  {#if data.seoDescription}
-    <meta name="description" content={data.seoDescription} />
-  {/if}
-  {#if data.postImageUrl}
-    <meta property="og:image" content={data.postImageUrl} />
-  {/if}
-</svelte:head>
 
 <div class="my-4 md:flex md:items-start md:gap-4">
   {#if data.rawPostImageUrl}