Custom post content blocks (images/gallery/video/quote) + backend-driven SEO settings

RichText.tsx switched to Payload's official React renderer + custom
JSXConverters (same call signature, LiveRichText/LivePostContent
untouched) — needed to render the new Lexical Blocks the Payload repo's
Posts.content just gained. Converters follow the existing CMS-image
convention (relative + aspect-[...] + fill + object-cover); the video
block resolves YouTube/Vimeo links to an iframe embed.

New getSeoSettings() fetcher (same pattern as getKleinunternehmer()),
app/layout.tsx now generateMetadata() reading it with the same fallback
values it used to hardcode. Per-post SEO overrides (seoTitle/
seoDescription/seoImage) wired into the blog detail page's metadata,
falling back to title/excerpt/thumbnail when empty.

Also fixed while auditing every page's metadata: missing descriptions on
3 konto pages, a static title on the dynamic order-detail route, and
missing OG images on /shop and /blog.

app/blog/[slug]/page.tsx

@@ -19,16 +19,29 @@ export async function generateMetadata({
   const post = await getPostBySlug(slug);
   if (!post) return { title: "Beitrag nicht gefunden" };
 
+  // Each falls back to the normal field when its SEO override (Posts.ts's
+  // "SEO" collapsible group) is empty — filling those in is optional, a
+  // post already has sensible metadata without them.
+  const title = post.seoTitle || post.title;
+  const description = post.seoDescription || post.excerpt;
+  const image = post.seoImage || post.thumbnail;
+
   return {
-    title: post.title,
-    description: post.excerpt,
+    title,
+    description,
     alternates: { canonical: `/blog/${post.slug}` },
     openGraph: {
-      title: `${post.title} | einfach produktiv.`,
-      description: post.excerpt,
+      title: `${title} | einfach produktiv.`,
+      description,
       url: `/blog/${post.slug}`,
       type: "article",
-      images: post.thumbnail ? [{ url: post.thumbnail }] : undefined,
+      images: image ? [{ url: image }] : undefined,
+    },
+    twitter: {
+      card: "summary_large_image",
+      title,
+      description,
+      images: image ? [image] : undefined,
     },
   };
 }