feat(invoice): per-line + cart discounts, fulfillment delivery date, pickup label, header layout refresh

- discounts: read discountedUnitPriceSet (per-line) and discountCode/discountCodes
  (order-level) from Shopify; render discounted unit price with strikethrough
  original on the invoice line and add a 'Rabattcode'/'Discount code' meta row
  when codes were used.
- delivery date: pick the latest fulfillment.createdAt for §11 UStG instead of
  hard-coding processedAt; fall back to invoice date when unfulfilled.
- pickup: detect Shopify Local Pickup (and 'Abholung'/'Pickup' custom rates) via
  shippingLine.source/code/title; suppress the pickup-location 'shipping address'
  block and render localized 'Abholung'/'Pick-up' as the shipping method.
- layout: move the company logo to the top-left and the meta block to the
  top-right, putting recipient (and any separate delivery address) on its own
  row below; drop the standalone invoice-/order-number meta rows and surface
  them inside the title (e.g. 'Rechnung Nr. RE-1004 · Bestellnummer: #1004') to
  recover vertical space.
- tests: smoke fixtures cover discount, pickup, and fulfillment-date variants
  without disturbing the AT B2B totals.

app/services/invoice/composeInvoice.ts

@@ -62,12 +62,18 @@ export function composeInvoice({
   });
   let notices = deriveNotices({ order, settings, isB2B });
 
-  const separateShippingAddress = mapSeparateShippingAddress(order);
-  const shippingMethod = order.shippingLine?.title?.trim() || undefined;
+  const isPickup = detectPickup(order.shippingLine);
+  const separateShippingAddress = isPickup ? undefined : mapSeparateShippingAddress(order);
+  const shippingMethod = isPickup
+    ? strings.pickupLabel
+    : order.shippingLine?.title?.trim() || undefined;
   const tracking = mapTracking(order);
 
   const invoiceDate = issueDate ?? new Date(order.processedAt ?? order.createdAt);
-  const deliveryDate = invoiceDate;
+  // §11 UStG: deliveryDate is the date goods/services were rendered. Prefer
+  // the latest fulfillment timestamp; fall back to invoice date when the
+  // order is unfulfilled (e.g. immediate-render services or digital orders).
+  const deliveryDate = pickDeliveryDate(order, invoiceDate);
   // For offers we treat `dueDate` as the offer's validity expiry (default 30
   // days from issue). The PDF renderer renders a different label.
   const dueDate = offer
@@ -86,6 +92,8 @@ export function composeInvoice({
     lines = lines.map((l) => ({
       ...l,
       unitPriceNet: -l.unitPriceNet,
+      originalUnitPriceNet:
+        l.originalUnitPriceNet != null ? -l.originalUnitPriceNet : undefined,
       totalNet: -l.totalNet,
     }));
     totals = {
@@ -125,6 +133,8 @@ export function composeInvoice({
     separateShippingAddress,
     shippingMethod,
     tracking,
+    discountCodes: order.discountCodes ?? [],
+    isPickup,
   };
 }
 
@@ -198,7 +208,13 @@ function mapLinesAndTotals(
 
   order.lineItems.forEach((li, idx) => {
     const qty = li.quantity;
-    const grossOrNetUnit = parseFloat(li.originalUnitPriceSet.shopMoney.amount);
+    // Prefer the post-discount unit price when Shopify provides one (it
+    // reflects both line-level and cart-level discount allocations). Fall
+    // back to original price when no discount applied.
+    const grossOrNetUnit = parseFloat(
+      (li.discountedUnitPriceSet ?? li.originalUnitPriceSet).shopMoney.amount,
+    );
+    const originalGrossOrNetUnit = parseFloat(li.originalUnitPriceSet.shopMoney.amount);
     // Total tax for this line summed across its tax lines.
     const lineTax = li.taxLines.reduce(
       (acc, t) => acc + parseFloat(t.priceSet.shopMoney.amount),
@@ -208,6 +224,17 @@ function mapLinesAndTotals(
     const lineGross = grossOrNetUnit * qty + (taxesIncluded ? 0 : lineTax);
     const lineNet = taxesIncluded ? grossOrNetUnit * qty - lineTax : grossOrNetUnit * qty;
     const unitNet = qty > 0 ? lineNet / qty : 0;
+    // For the strikethrough original, compute net the same way the line is
+    // computed: when taxesIncluded, derive an equivalent net per unit using
+    // the line's effective tax rate; when not, the original IS the net.
+    const effectiveRate = qty > 0 && grossOrNetUnit > 0
+      ? lineTax / (grossOrNetUnit * qty)
+      : 0;
+    const originalUnitNet = taxesIncluded
+      ? originalGrossOrNetUnit / (1 + effectiveRate)
+      : originalGrossOrNetUnit;
+    const hasDiscount =
+      Math.round(originalGrossOrNetUnit * 100) !== Math.round(grossOrNetUnit * 100);
 
     linesOut.push({
       position: idx + 1,
@@ -215,6 +242,7 @@ function mapLinesAndTotals(
       sku: li.sku ?? undefined,
       quantity: qty,
       unitPriceNet: round2(unitNet),
+      originalUnitPriceNet: hasDiscount ? round2(originalUnitNet) : undefined,
       totalNet: round2(lineNet),
       imageUrl: li.imageUrl ?? undefined,
     });
@@ -452,3 +480,37 @@ function mapTracking(order: RawOrderForInvoice): TrackingInfo[] {
   }
   return out;
 }
+
+/**
+ * Heuristically detects whether the order's shipping line is a "local
+ * pickup" line. Shopify exposes pickup either via the dedicated Local
+ * Pickup app (source contains "pickup") or via a custom rate the merchant
+ * named "Abholung"/"Pickup". When detected, callers should NOT render the
+ * pickup-location address as a separate "delivery address".
+ */
+function detectPickup(shippingLine: RawShippingLine | null): boolean {
+  if (!shippingLine) return false;
+  const haystack = [
+    shippingLine.source,
+    shippingLine.code,
+    shippingLine.title,
+    shippingLine.carrierIdentifier,
+  ]
+    .filter(Boolean)
+    .join(" ")
+    .toLowerCase();
+  return /pick[\s-]?up|abholung|abhol\b/.test(haystack);
+}
+
+/**
+ * Picks the delivery date for §11 UStG: the latest fulfillment timestamp
+ * when the order is fulfilled, otherwise the invoice date itself (best
+ * approximation for unfulfilled / digital orders).
+ */
+function pickDeliveryDate(order: RawOrderForInvoice, invoiceDate: Date): Date {
+  const stamps = (order.fulfillments ?? [])
+    .map((f) => (f.createdAt ? new Date(f.createdAt).getTime() : NaN))
+    .filter((n) => Number.isFinite(n));
+  if (stamps.length === 0) return invoiceDate;
+  return new Date(Math.max(...stamps));
+}