feat(billing): 80mm thermal invoice layout (ADD-P001)

GET billing/invoices/:id/document?format=thermal renders a dedicated 80mm
receipt template (72mm printable, 4mm margins each side), not a CSS variant
of the A4 layout — the A4 CSS is absolutely-positioned/fixed-px, tuned for a
210mm page, and doesn't reflow at thermal width. No seal (not a thermal
convention, renders badly on 1-bit thermal heads); line items stack
(description, then qty x rate = amount) instead of a table, since a real
table leaves ~10-14 chars for description at this width.

PdfRenderService gains a thermal render path: full 80mm-width viewport,
content height measured via page.evaluate after settle (continuous-roll
receipts have no fixed page length), and a noFallback option — a Chromium
failure throws a clear error instead of silently degrading to the generic
A4/no-QR fallback, which would hand back a different document than what was
asked for. The frontend surfaces that as a toast pointing at the existing A4
download.

format is strictly validated (a4|thermal only, BadRequestException
otherwise), not silently coerced.

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

apps/edr-freight-web/backoffice/src/services/invoices.service.ts

@@ -29,9 +29,11 @@ export const invoicesService = {
       .then((r) => r.data);
   },
 
-  downloadDocument(id: string) {
+  /** `format` omitted or "a4" → standard A4 PDF; "thermal" → 80mm thermal layout (ADD-P001). */
+  downloadDocument(id: string, format?: "a4" | "thermal") {
     return apiClient.get<Blob>(URL_CONSTANTS.BILLING.INVOICE_DOCUMENT(id), {
       responseType: "blob",
+      params: format ? { format } : undefined,
     });
   },