feat: add database export and import functionality with user confirmation

public/js/main.js

@@ -3215,6 +3215,115 @@ async function handleExportPDF() {
   }
 }
 
+/**
+ * Export entire database
+ */
+async function exportDatabase() {
+  try {
+    // Fetch all data
+    const entries = await fetchEntries();
+    const settings = {
+      employeeName: await getSetting('employeeName') || '',
+      employeeId: await getSetting('employeeId') || '',
+      bundesland: await getSetting('bundesland') || 'NW',
+      vacationDaysPerYear: await getSetting('vacationDaysPerYear') || 30
+    };
+    
+    // Create export object
+    const exportData = {
+      version: '1.0',
+      exportDate: new Date().toISOString(),
+      entries: entries,
+      settings: settings
+    };
+    
+    // Convert to JSON
+    const jsonString = JSON.stringify(exportData, null, 2);
+    const blob = new Blob([jsonString], { type: 'application/json' });
+    
+    // Create download link
+    const url = URL.createObjectURL(blob);
+    const a = document.createElement('a');
+    a.href = url;
+    a.download = `zeiterfassung_backup_${new Date().toISOString().split('T')[0]}.json`;
+    document.body.appendChild(a);
+    a.click();
+    document.body.removeChild(a);
+    URL.revokeObjectURL(url);
+    
+    showNotification(`Datenbank exportiert: ${entries.length} Einträge`, 'success');
+  } catch (error) {
+    console.error('Error exporting database:', error);
+    showNotification('Fehler beim Exportieren der Datenbank', 'error');
+  }
+}
+
+/**
+ * Import entire database
+ */
+async function importDatabase(file) {
+  try {
+    const text = await file.text();
+    const importData = JSON.parse(text);
+    
+    // Validate data structure
+    if (!importData.entries || !Array.isArray(importData.entries)) {
+      throw new Error('Ungültiges Datenbankformat');
+    }
+    
+    // Confirm before overwriting
+    const confirmed = confirm(
+      `Möchten Sie die Datenbank wirklich importieren?\n\n` +
+      `Dies wird alle ${importData.entries.length} Einträge importieren und vorhandene Daten überschreiben.\n\n` +
+      `Export-Datum: ${new Date(importData.exportDate).toLocaleString('de-DE')}`
+    );
+    
+    if (!confirmed) {
+      return;
+    }
+    
+    // Delete all existing entries
+    const existingEntries = await fetchEntries();
+    for (const entry of existingEntries) {
+      await fetch(`/api/entries/${entry.id}`, { method: 'DELETE' });
+    }
+    
+    // Import entries
+    let imported = 0;
+    for (const entry of importData.entries) {
+      try {
+        // Remove ID to create new entries
+        const { id, ...entryData } = entry;
+        await fetch('/api/entries', {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify(entryData)
+        });
+        imported++;
+      } catch (err) {
+        console.error('Error importing entry:', err);
+      }
+    }
+    
+    // Import settings
+    if (importData.settings) {
+      await setSetting('employeeName', importData.settings.employeeName || '');
+      await setSetting('employeeId', importData.settings.employeeId || '');
+      await setSetting('bundesland', importData.settings.bundesland || 'NW');
+      await setSetting('vacationDaysPerYear', importData.settings.vacationDaysPerYear || 30);
+      await loadSettings(); // Reload settings to UI
+    }
+    
+    // Reload view
+    await reloadView();
+    
+    showNotification(`Datenbank importiert: ${imported} Einträge`, 'success');
+  } catch (error) {
+    console.error('Error importing database:', error);
+    showNotification('Fehler beim Importieren der Datenbank: ' + error.message, 'error');
+  }
+}
+
 /**
  * Show a temporary notification
  */
@@ -3535,6 +3644,19 @@ function initializeEventListeners() {
     showNotification('Personalnummer gespeichert', 'success');
   });
   
+  // Database export/import
+  document.getElementById('btnExportDB').addEventListener('click', exportDatabase);
+  document.getElementById('btnImportDB').addEventListener('click', () => {
+    document.getElementById('importDBFile').click();
+  });
+  document.getElementById('importDBFile').addEventListener('change', (e) => {
+    const file = e.target.files[0];
+    if (file) {
+      importDatabase(file);
+      e.target.value = ''; // Reset file input
+    }
+  });
+  
   // Close modal when clicking outside
   document.getElementById('entryModal').addEventListener('click', (e) => {
     if (e.target.id === 'entryModal') {