feat: add buildPdf for cashbox export

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

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

@@ -1,4 +1,4 @@
-import { buildCsv, buildRows } from './cashbox-export.utils';
+import { buildCsv, buildPdf, buildRows } from './cashbox-export.utils';
 
 describe('buildRows', () => {
   const team = (overrides: Partial<{ transactions: any[]; players: any[] }> = {}) => ({
@@ -167,3 +167,26 @@ describe('buildCsv', () => {
     );
   });
 });
+
+describe('buildPdf', () => {
+  it('produces a non-empty valid PDF buffer', async () => {
+    const buffer = await buildPdf(
+      { name: 'Team A' } as any,
+      [
+        { date: '2026-08-05T00:00:00.000Z', type: 'payment', who: 'Alex Muster', note: 'Bar bezahlt', amount: 10, runningTotal: 10 },
+      ],
+      '2026-08-01',
+      '2026-08-31',
+    );
+
+    expect(Buffer.isBuffer(buffer)).toBe(true);
+    expect(buffer.length).toBeGreaterThan(100);
+    expect(buffer.subarray(0, 5).toString('utf-8')).toBe('%PDF-');
+  });
+
+  it('still produces a valid PDF when there are no rows', async () => {
+    const buffer = await buildPdf({ name: 'Team A' } as any, [], '2026-08-01', '2026-08-31');
+
+    expect(buffer.subarray(0, 5).toString('utf-8')).toBe('%PDF-');
+  });
+});

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

@@ -1,4 +1,6 @@
 import { Team } from 'src/teams/entities/team.entity';
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const PDFDocument = require('pdfkit');
 
 export interface CashboxExportRow {
   date: string;
@@ -100,3 +102,35 @@ export function buildCsv(rows: CashboxExportRow[]): string {
   }
   return lines.join('\r\n');
 }
+
+export function buildPdf(
+  team: Pick<Team, 'name'>,
+  rows: CashboxExportRow[],
+  from: string,
+  to: string,
+): Promise<Buffer> {
+  return new Promise((resolve, reject) => {
+    const doc = new PDFDocument({ margin: 40 });
+    const chunks: Buffer[] = [];
+    doc.on('data', (chunk) => chunks.push(chunk));
+    doc.on('end', () => resolve(Buffer.concat(chunks)));
+    doc.on('error', reject);
+
+    doc.fontSize(16).text(`Kassenbuch ${team.name}`);
+    doc.fontSize(10).text(`Zeitraum: ${from} bis ${to}`);
+    doc.moveDown();
+
+    if (rows.length === 0) {
+      doc.text('Keine Buchungen im gewählten Zeitraum.');
+    } else {
+      for (const row of rows) {
+        doc.text(
+          `${row.date.slice(0, 10)}  ${TYPE_LABELS[row.type] ?? row.type}  ${row.who}  ${row.note}  ` +
+            `${formatGermanAmount(row.amount)} €  Saldo: ${formatGermanAmount(row.runningTotal)} €`,
+        );
+      }
+    }
+
+    doc.end();
+  });
+}