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/api/checkout/route.ts

@@ -9,6 +9,18 @@ import { describeBundleContents } from "../../lib/bundleContents";
 import { sendCriticalAlert } from "../../lib/alertAdmin";
 import { sendOrderConfirmationEmail } from "../../lib/orderEmail";
 
+// Plain float arithmetic on money (quantity × unitPrice summed across
+// lines, a percent discount, subtracting/adding those together) drifts
+// into results like 84.30000000000001 — cosmetically invisible wherever
+// formatPrice()'s toFixed(2) already rounds for display, but stored as-is
+// on the order otherwise, which is where it actually showed up (Payload's
+// admin list/edit view for a plain number field has no such formatting).
+// Rounded once here, right before persisting, rather than chasing it down
+// at every downstream display site.
+function roundMoney(amount: number): number {
+  return Math.round(amount * 100) / 100;
+}
+
 type CheckoutBody = {
   cart: CartItem[];
   shippingMethodId: number;
@@ -160,7 +172,7 @@ export async function POST(request: Request) {
       variantName: variant?.name ?? null,
     });
   }
-  const subtotal = items.reduce((sum, i) => sum + i.quantity * i.unitPrice, 0);
+  const subtotal = roundMoney(items.reduce((sum, i) => sum + i.quantity * i.unitPrice, 0));
 
   const shippingMethods = await getShippingMethods();
   const shippingMethod = shippingMethods.find((m) => m.id === body.shippingMethodId);
@@ -178,10 +190,11 @@ export async function POST(request: Request) {
     if (!validation.valid) return NextResponse.json({ ok: false, reason: validation.reason }, { status: 400 });
     const redeemed = await redeemDiscountCode(validation.doc);
     if (!redeemed) return NextResponse.json({ ok: false, reason: "Rabattcode konnte nicht eingelöst werden." }, { status: 400 });
-    discountAmount =
-      validation.doc.type === "percent" ? (subtotal * validation.doc.value) / 100 : Math.min(validation.doc.value, subtotal);
+    discountAmount = roundMoney(
+      validation.doc.type === "percent" ? (subtotal * validation.doc.value) / 100 : Math.min(validation.doc.value, subtotal),
+    );
   }
-  const total = Math.max(0, subtotal - discountAmount) + shippingCost;
+  const total = roundMoney(Math.max(0, subtotal - discountAmount) + shippingCost);
 
   const order = await createOrder({
     customerId: customer.id,

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