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-api/src/modules/billing/documents/invoice-document.service.spec.ts

@@ -44,3 +44,46 @@ describe("InvoiceDocumentService.buildHtml — EIMS QR", () => {
     );
   });
 });
+
+describe("InvoiceDocumentService.buildThermalHtml", () => {
+  const service = new InvoiceDocumentService({} as never, {} as never, {} as never);
+
+  it("renders no seal markup at all — dropped for thermal, not shrunk", () => {
+    const html = service.buildThermalHtml(model());
+    expect(html).not.toContain('class="seal"');
+    expect(html).not.toContain("seal-image");
+  });
+
+  it("renders the QR image when qrImageUrl is set, centered rather than absolutely positioned", () => {
+    const html = service.buildThermalHtml(model({ qrImageUrl: "data:image/png;base64,QR" }));
+    expect(html).toContain('class="qr"');
+    expect(html).toContain('src="data:image/png;base64,QR"');
+    expect(html).not.toContain("position: absolute");
+  });
+
+  it("wraps a long IRN summary value rather than truncating it", () => {
+    const irn = "9fe9bbbece6ab76c112b617534e6aac7aa8b819d5be79f4d3d088ed2e887b2e0";
+    const html = service.buildThermalHtml(model({ summary: [{ label: "EIMS IRN", value: irn }] }));
+    expect(html).toContain(irn);
+    expect(html).toContain("overflow-wrap: anywhere");
+  });
+
+  it("renders a line item as stacked description + qty x rate = amount, not a table row", () => {
+    const html = service.buildThermalHtml(
+      model({
+        lines: [{ description: "40ft container rail freight", quantity: 12, unitRate: 245683.95, amount: 2948207.4 }],
+      }),
+    );
+    expect(html).not.toContain("<table");
+    expect(html).not.toContain("<td");
+    expect(html).toContain("40ft container rail freight");
+    expect(html).toContain("12 x");
+    expect(html).toContain("2,948,207.4 Birr (ETB)");
+  });
+
+  it("uses fluid, full-width layout — no fixed-px A4 geometry", () => {
+    const html = service.buildThermalHtml(model());
+    expect(html).not.toContain("width: 330px");
+    expect(html).not.toContain("right: 160px");
+  });
+});