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.

package.json

@@ -12,6 +12,7 @@
   "dependencies": {
     "@einfach-produktiv/invoicing": "git+https://git.mk360.de/Marco/einfach-produktiv-invoicing.git#main",
     "@payloadcms/live-preview-react": "^3.85.2",
+    "@payloadcms/richtext-lexical": "^3.85.2",
     "@react-pdf/renderer": "^4.5.1",
     "motion": "^12.42.2",
     "next": "16.2.9",