fix: export filtered tender list as real XLSX

tests/tender-workbook.test.mjs

@@ -0,0 +1,21 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import ExcelJS from 'exceljs';
+import {createTenderWorkbook} from '../src/services/tenderWorkbook.js';
+test('list XLSX roundtrip preserves all rows, Turkish text, special characters and text-only cells',async()=>{
+  const rows=Array.from({length:125},(_,i)=>({ikn:`2026/00${i}`,baslik:i===0?'=1+1':'İğdır, "Kit"\nTest # &',
+    kurum:'Sağlık',sehir:'Iğdır',tarih:'01.10.2026',saat:'09:30',cpv:['001','002'],kaynakUrl:'https://example.test/?a=1&b=2#ilan'}));
+  const bytes=await createTenderWorkbook(rows);
+  assert.equal(Buffer.from(bytes).subarray(0,2).toString(),'PK');
+  const book=new ExcelJS.Workbook();await book.xlsx.load(bytes);
+  const sheet=book.getWorksheet('İhale Listesi');
+  assert.equal(sheet.rowCount,126);
+  assert.equal(sheet.getCell('A2').value,'2026/000');
+  assert.equal(sheet.getCell('B2').value,'=1+1');
+  assert.equal(sheet.getCell('B2').type,ExcelJS.ValueType.String);
+  assert.equal(sheet.getCell('B126').value,rows[124].baslik);
+  assert.equal(sheet.getCell('F2').value,'09:30');
+  assert.equal(sheet.getCell('I2').value,'001, 002');
+  assert.equal(sheet.getCell('J2').value,rows[0].kaynakUrl);
+  await assert.rejects(()=>createTenderWorkbook([]),/bulunamadı/);
+});