Follow Products.description consolidation to richText-only

Backend dropped the plain-text description field in favor of a single
richText one (see docker/payload commit 1ba8d07). Renders formatted
(bold/italic/multiple paragraphs) via the shared RichText component on
the PDP (der-eine, tasse-die-pause); everywhere else (Passend-dazu cards,
Product JSON-LD, homepage spotlight fallback) derives plain text at read
time via a new extractPlainText() helper instead of a second field.
Removes the description line from cart line items entirely — it only
bloated the cart with no real benefit there.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J1Hu5bZ1kZUgKhab6yNwCt

app/components/ProductSpotlight.tsx

@@ -134,7 +134,7 @@ export async function ProductSpotlight() {
           >
             {product.spotlightHeadline || product.name}
           </p>
-          <SpotlightText content={product.spotlightText} fallback={product.description} />
+          <SpotlightText content={product.spotlightText} fallback={product.descriptionText} />
           {/* MwSt./Versand disclosure on its own line, not crammed into
               the price row itself — same reasoning as todo-cards'
               Pricing.tsx (identical text, same narrow-column risk). */}