Fix several mobile responsive issues across Hero, Newsletter, cart, and Challenge

- Hero CTA: back to a single line below lg: (wrapping put the icon
  beside two lines and looked broken), sized down instead so the full
  phrase fits.
- Hero heading: dropped the forced <br> after "darf" at true mobile
  widths, kept it only for the sm-lg tablet range it was added for.
- Hero social proof: avatars+text now wrap and center instead of
  cramming onto one row (flex-wrap + justify-center, no fixed
  breakpoint needed).
- Newsletter card icon: stacked above the copy and centered below md:
  instead of squeezed into a row beside it.
- TrustRow: left-aligned below md: instead of centered (shop, cart, and
  every other page using this component).
- Cart line item image: full width below sm: instead of a fixed 150px
  square.
- Challenge EmailCapture (top + bottom CTA, same shared component):
  input and button stack full-width below sm: instead of squeezing
  into one row.
- Challenge steps: icon above text and centered at every breakpoint
  (previously only from lg: up), connector arrows centered to match.

app/components/TrustRow.tsx

@@ -11,7 +11,7 @@ export async function TrustRow() {
   if (items.length === 0) return null;
 
   return (
-    <div className="w-full bg-bg-base flex flex-col md:flex-row gap-6 md:gap-12 items-center justify-center py-8 px-[var(--layout-padding-x)]">
+    <div className="w-full bg-bg-base flex flex-col md:flex-row gap-6 md:gap-12 items-start md:items-center justify-center py-8 px-[var(--layout-padding-x)]">
       {items.map((item, i) => (
         <div key={item.id} className="flex items-center gap-6 md:gap-12">
           {i > 0 && <div className="hidden md:block h-10 w-px bg-border" />}