PDP hero: plain checkmarks for usps; spotlight image now links to PDP

- product.usps rendered via STEP_ICONS[usp.icon] (checkCircle — a
  circled glyph), inconsistent with the plain checkmark every other
  feature-bullet list on the site uses (der-eine's own original
  Hero.tsx, RichText/PageBlocks' own checklists). Reused PageBlocks'
  CheckIcon (now exported) instead — usp.icon stays stored, just
  unused for this particular list (reported 2026-08-30).
- ProductSpotlight's image had no link at all — every other product
  card (ProductGrid, RelatedProducts, MerklisteGrid, via ProductCard)
  already makes its image clickable. Same Link-wraps-only-the-image
  pattern as ProductCard.tsx (WishlistButton stays an unnested sibling).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Eg6h91yngXmSnM51wxXM8

app/components/PageBlocks.tsx

@@ -274,7 +274,7 @@ export function renderPageBlockSync(block: PageBlock): React.ReactNode {
 
 // Same checkmark used by /lebensuhr's and /7-tage-klarheits-check's own
 // checklists.
-function CheckIcon() {
+export function CheckIcon() {
   return (
     <svg width="18" height="18" viewBox="0 0 18 18" fill="none" className="shrink-0 mt-1">
       <path d="M3 9.5l4 4L15 4" stroke="#f6a701" strokeWidth="2.2" strokeLinecap="round" strokeLinejoin="round" />