Fix money rounding drift, low-stock hint spacing, spotlight CTA height mismatch

- Round subtotal/discountAmount/total to 2 decimals before persisting an
  order — float arithmetic on money was drifting into values like
  84.30000000000001, invisible wherever a display already ran it through
  toFixed(2), but stored as-is and visible raw in the Payload admin's
  plain number field
- Low-stock hint now uses gap-1 consistently (was gap-2) in both
  AddToCartButton/AddToCartInlineButton, for smaller/consistent spacing
  above it regardless of context
- ProductSpotlight's CTA row now uses items-start at sm: — without it,
  default cross-axis stretch made "Mehr erfahren" grow to match
  AddToCartButton's height whenever the low-stock hint made that one
  taller, so the link visibly looked "fatter" than the actual button

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/components/AddToCartButton.tsx

@@ -81,7 +81,7 @@ export function AddToCartButton({
   const displayLabel = currentlyOutOfStock ? "Ausverkauft" : label;
 
   return (
-    <div className="flex flex-col gap-2">
+    <div className="flex flex-col gap-1">
       {variants.length > 0 && (
         <select
           value={selectedVariant}

app/components/AddToCartInlineButton.tsx

@@ -77,7 +77,7 @@ export function AddToCartInlineButton({
       : "border-border hover:border-brand";
 
   return (
-    <div className="flex flex-col gap-2 w-full">
+    <div className="flex flex-col gap-1 w-full">
       {variants.length > 0 && (
         <select
           value={selectedVariant}

app/components/ProductSpotlight.tsx

@@ -91,7 +91,13 @@ export async function ProductSpotlight() {
               Lieferzeit: {shipping.totalDays.min}–{shipping.totalDays.max} Werktage innerhalb Deutschlands
             </p>
           </div>
-          <div className="flex flex-col sm:flex-row gap-3 w-full sm:w-auto">
+          {/* items-start at sm: — without it, the default cross-axis
+              stretch makes "Mehr erfahren" grow to match
+              AddToCartButton's own height whenever that one gets taller
+              (e.g. the low-stock hint line pushing its content down), so
+              a plain text link visibly ends up "fatter" than the actual
+              button next to it. */}
+          <div className="flex flex-col sm:flex-row items-stretch sm:items-start gap-3 w-full sm:w-auto">
             {/* No className override — the section's bg is bg-bg-base now
                 (matches Tools/Blog above/below), same as AddToCartButton's
                 own default styling/ring-offset, so no override is needed