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/loadDraftOrderForOffer.server.ts

@@ -163,6 +163,7 @@ export async function loadDraftOrderForOffer(
     paymentGatewayNames: [],
     shippingLine: null,
     fulfillments: [],
+    discountCodes: [],
     taxesIncluded: draft.taxesIncluded,
     customer: draft.customer,
     billingAddress: draft.billingAddress,
@@ -178,6 +179,7 @@ export async function loadDraftOrderForOffer(
         sku: node.sku,
         quantity: node.quantity,
         originalUnitPriceSet: node.originalUnitPriceSet,
+        discountedUnitPriceSet: null,
         taxLines: node.taxLines,
         imageUrl: node.image?.url ?? null,
       };