Enhance Excel export functionality in backend and frontend; implement Excel file generation and update download logic for correct file extension

backend/package.json

@@ -16,23 +16,23 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "express": "^4.18.2",
-    "cors": "^2.8.5",
-    "helmet": "^7.1.0",
-    "morgan": "^1.10.0",
-    "dotenv": "^16.3.1",
-    "mysql2": "^3.6.5",
-    "sequelize": "^6.35.2",
     "bcrypt": "^5.1.1",
-    "jsonwebtoken": "^9.0.2",
-    "nodemailer": "^6.9.7",
+    "cors": "^2.8.5",
     "crypto": "^1.0.1",
+    "dotenv": "^16.3.1",
+    "exceljs": "^4.4.0",
+    "express": "^4.18.2",
+    "express-session": "^1.18.0",
+    "helmet": "^7.1.0",
+    "jsonwebtoken": "^9.0.2",
+    "morgan": "^1.10.0",
+    "mysql2": "^3.6.5",
+    "nodemailer": "^6.9.7",
     "passport": "^0.7.0",
     "passport-google-oauth20": "^2.0.0",
-    "express-session": "^1.18.0"
+    "sequelize": "^6.35.2"
   },
   "devDependencies": {
     "nodemon": "^3.0.2"
   }
 }
-

backend/src/controllers/ExportController.js

@@ -34,7 +34,7 @@ class ExportController {
   }
 
   /**
-   * Exportiert Daten als Excel
+   * Exportiert Daten als Excel (.xlsx)
    */
   async exportExcel(req, res) {
     try {
@@ -47,11 +47,11 @@ class ExportController {
         });
       }
       
-      const excel = await ExportService.exportExcel(userId, startDate, endDate);
+      const buffer = await ExportService.exportExcel(userId, startDate, endDate);
       
-      res.setHeader('Content-Type', 'text/csv; charset=utf-8');
-      res.setHeader('Content-Disposition', `attachment; filename="zeiterfassung_${startDate}_${endDate}.csv"`);
-      res.send(excel);
+      res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+      res.setHeader('Content-Disposition', `attachment; filename="zeiterfassung_${startDate}_${endDate}.xlsx"`);
+      res.send(buffer);
     } catch (error) {
       console.error('Fehler beim Excel-Export:', error);
       res.status(500).json({ 

backend/src/services/ExportService.js

@@ -29,17 +29,49 @@ class ExportService {
   }
 
   /**
-   * Exportiert Daten als Excel (CSV mit Excel-kompatiblem Encoding)
+   * Exportiert Daten als echte Excel-Datei (.xlsx)
    * @param {number} userId - User-ID
    * @param {string} startDate - Startdatum
    * @param {string} endDate - Enddatum
-   * @returns {Promise<string>} Excel-kompatibles CSV mit BOM
+   * @returns {Promise<Buffer>} Excel-Datei als Buffer
    */
   async exportExcel(userId, startDate, endDate) {
-    const csv = await this.exportCSV(userId, startDate, endDate);
+    const ExcelJS = require('exceljs');
+    const data = await this._getExportData(userId, startDate, endDate);
     
-    // UTF-8 BOM für Excel
-    return '\ufeff' + csv;
+    // Erstelle Workbook
+    const workbook = new ExcelJS.Workbook();
+    const worksheet = workbook.addWorksheet('Zeiterfassung');
+    
+    // Definiere Spalten
+    worksheet.columns = [
+      { header: 'Datum', key: 'date', width: 12 },
+      { header: 'Uhrzeit', key: 'time', width: 10 },
+      { header: 'Aktivität', key: 'activity', width: 20 },
+      { header: 'Gesamt-Netto-Arbeitszeit', key: 'netWorkTime', width: 25 }
+    ];
+    
+    // Style für Header
+    worksheet.getRow(1).font = { bold: true };
+    worksheet.getRow(1).fill = {
+      type: 'pattern',
+      pattern: 'solid',
+      fgColor: { argb: 'FFE0E0E0' }
+    };
+    
+    // Füge Daten hinzu
+    data.forEach(row => {
+      worksheet.addRow({
+        date: row.date,
+        time: row.time,
+        activity: row.activity,
+        netWorkTime: row.netWorkTime
+      });
+    });
+    
+    // Generiere Buffer
+    const buffer = await workbook.xlsx.writeBuffer();
+    return buffer;
   }
 
   /**