feat(treasury): list debtors and creditors on the finance report

Show open receivable and payable balances on separate report tabs, and include each list in an Excel export.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/treasury/treasury.controller.ts

@@ -269,7 +269,11 @@ export class TreasuryController {
     @Query('from') from?: string,
     @Query('to') to?: string,
   ) {
-    const buffer = await this.ops.reportExcel(user, from, to);
+    const [debtors, creditors] = await Promise.all([
+      this.treasury.partyBalances(user, 'income'),
+      this.treasury.partyBalances(user, 'expense'),
+    ]);
+    const buffer = await this.ops.reportExcel(user, from, to, { debtors, creditors });
     return new StreamableFile(buffer, {
       type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
       disposition: 'attachment; filename="treasury-report.xlsx"',