Revert checkout step-number circle borders to the original color

Only the connector line between steps stays the darker #c4b8a0 —
the number circles themselves go back to border-border per feedback.

app/components/CheckoutSteps.tsx

@@ -20,12 +20,9 @@ function StepCircle({ state, number }: { state: StepState; number: number }) {
     );
   }
   return (
-    // border-[#c4b8a0], not the shared border-border (#e5e0d8) — nearly the
-    // same luminance as the page's own bg-bg-base (#f8f5f1), barely visible
-    // (fixed 2026-07-24, feedback: "die Striche bei den Nummern-Steps sind
-    // zu hell"). Same color as the connector line below and the checkout
-    // step cards' own border fix, for consistency.
-    <div className="flex size-9 items-center justify-center rounded-full border border-[#c4b8a0] font-bold text-body-sm text-text-muted">
+    // Back to the shared border-border (reverted 2026-07-24 per feedback —
+    // only the connector line below should be the darker #c4b8a0).
+    <div className="flex size-9 items-center justify-center rounded-full border border-border font-bold text-body-sm text-text-muted">
       {number}
     </div>
   );