fix(invoice): suppress GiroCode + payment terms for refunded (and paid) orders

User reported that fully refunded orders still rendered a SEPA GiroCode
QR asking the customer to wire the original total. The existing gate
("!viewModel.paid") only excluded literally-PAID orders; REFUNDED,
PARTIALLY_REFUNDED, VOIDED, AUTHORIZED, etc. all sneaked through and
produced a confusing payment request for an order whose outstanding
balance is in fact 0.

Root cause: the view model exposed two related but ambiguous flags
("paid" and "paymentStatus") and the renderer mixed them
inconsistently. Both the GiroCode generation step in
generateInvoice.server.tsx AND the GiroCode/payment-terms render gates
in InvoiceDocument.tsx checked the wrong one.

Fix: introduce a single derived "requiresPayment" flag on the view
model (composeInvoice.ts) that is true only when:
  - the document is a regular invoice (not a storno or an offer), AND
  - paymentStatus is neither "paid" nor "refunded".

That single flag now drives:
  - GiroCode QR generation (skip QR fetch for paid/refunded)
  - GiroCode block render in the PDF
  - payment-terms paragraph render in the PDF

The existing "Zahlstatus: Erstattet" / "Payment status: Refunded"
meta-row continues to communicate the refund visually — the change
just removes the contradictory call-to-pay.

Side benefits:
  - Storno (cancellation invoice) PDFs no longer emit the German
    "Bitte überweise …" payment-terms paragraph (kind=storno was
    falling through the same not-paid branch).
  - Same suppression for fully PAID orders (covered by a second smoke
    fixture) so the QR doesn't suggest re-payment after the fact.

Verification: new smoke fixtures (REFUNDED + PAID) build a real
GiroCode data URL and verify the PDF text neither contains the
"GiroCode" caption nor the "Bitte überweise" German payment terms,
while still showing the corresponding "Erstattet" / "Bezahlt" status
row. tsc / smoke / tests / build all green.

app/services/invoice/generateInvoice.server.tsx

@@ -95,12 +95,15 @@ export async function generateInvoice(
   // Product images for each line (best-effort, parallel, in-process cache).
   await attachLineItemImages(viewModel.lines);
 
-  // GiroCode (only for invoices that are unpaid + IBAN configured + enabled).
+  // GiroCode (only when the invoice is actually outstanding + IBAN
+  // configured + enabled). `requiresPayment` already encodes "regular
+  // invoice AND money still owed" — so paid, refunded, storno and
+  // offer documents all skip QR generation and the PDF stays tidy.
   if (
     kind === "invoice" &&
     settings.giroCodeEnabled &&
     settings.iban &&
-    !viewModel.paid &&
+    viewModel.requiresPayment &&
     viewModel.totals.gross > 0
   ) {
     viewModel.giroCodePngDataUrl = await buildGiroCodeDataUrl({