address code review: assert page count in multi-page test, document fixes

- Lock in the exact expected page count (4) for the 60+60-row pagination
  test, which previously only checked the buffer was non-trivial. This is
  the scenario most likely to expose a footer/pagination regression.
- Add short comments explaining the footerY height-bound fix and the
  pdfPageCount() regex's coupling to pdfkit's serialization format.

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

myteamwallet_backend/src/cashbox-export/cashbox-export.utils.spec.ts

@@ -1,5 +1,8 @@
 import { buildCsv, buildPdf, buildReceivableRows, buildRows } from './cashbox-export.utils';
 
+// Reads the page count directly out of the raw PDF bytes instead of pulling in
+// a parser dependency. Coupled to pdfkit's current /Pages dict serialization -
+// a pdfkit upgrade that reorders/reflows it could require adjusting this regex.
 function pdfPageCount(buffer: Buffer): number {
   const match = buffer.toString('latin1').match(/\/Type\s*\/Pages[\s\S]{0,80}?\/Count\s+(\d+)/);
   if (!match) throw new Error('Could not find page count in PDF buffer');
@@ -344,5 +347,8 @@ describe('buildPdf', () => {
 
     expect(buffer.subarray(0, 5).toString('utf-8')).toBe('%PDF-');
     expect(buffer.length).toBeGreaterThan(2000);
+    // Guards against the footer loop reintroducing blank trailing pages: with
+    // the bug, this dataset produced 12 pages (3x the real content pages).
+    expect(pdfPageCount(buffer)).toBe(4);
   });
 });

myteamwallet_backend/src/cashbox-export/cashbox-export.utils.ts

@@ -313,6 +313,12 @@ function addFooters(doc: PDFKit.PDFDocument, teamName: string): void {
   for (let i = range.start; i < range.start + range.count; i++) {
     doc.switchToPage(i);
     const footerY = doc.page.height - 25;
+    // footerY sits inside the reserved bottom margin (below pdfkit's page
+    // maxY()). Without an explicit `height`, pdfkit's LineWrapper measures
+    // overflow against the full-page maxY() and calls addPage() here on every
+    // iteration - silently appending blank trailing pages. Bounding the text
+    // to its own small box (well over the 8pt single-line height needed)
+    // keeps the overflow check local and stops that auto-pagination.
     doc
       .fontSize(8)
       .font('Helvetica')