🔧 Update: Enhanced error handling and logging across various modules

**Änderungen:**
- ✅ app.py: Hinzugefügt, um CSRF-Fehler zu behandeln
- ✅ models.py: Fehlerprotokollierung bei der Suche nach Gastanfragen per OTP
- ✅ api.py: Fehlerprotokollierung beim Markieren von Benachrichtigungen als gelesen
- ✅ calendar.py: Fallback-Daten zurückgeben, wenn keine Kalenderereignisse vorhanden sind
- ✅ guest.py: Status-Check-Seite für Gäste aktualisiert
- ✅ hardware_integration.py: Debugging-Informationen für erweiterte Geräteinformationen hinzugefügt
- ✅ tapo_status_manager.py: Rückgabewert für Statusabfrage hinzugefügt

**Ergebnis:**
- Verbesserte Fehlerbehandlung und Protokollierung für eine robustere Anwendung
- Bessere Nachverfolgbarkeit von Fehlern und Systemverhalten

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

backend/static/js/admin-guest-requests.js

@@ -339,6 +339,24 @@ function createRequestRow(request) {
                         </button>
                     ` : ''}
                     
+                    ${request.status === 'approved' ? `
+                        <button onclick="showOtpCode(${request.id})" 
+                                class="text-blue-600 hover:text-blue-900 dark:text-blue-400 dark:hover:text-blue-300 transition-colors"
+                                title="OTP-Code anzeigen">
+                            <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 7a2 2 0 012 2m4 0a6 6 0 01-7.743 5.743L11 17H9v2H7v2H4a1 1 0 01-1-1v-3a1 1 0 011-1h2.586l6.243-6.243A6 6 0 0121 9z"/>
+                            </svg>
+                        </button>
+                        
+                        <button onclick="revokeRequest(${request.id})" 
+                                class="text-orange-600 hover:text-orange-900 dark:text-orange-400 dark:hover:text-orange-300 transition-colors"
+                                title="Genehmigung widerrufen">
+                            <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M18.364 18.364A9 9 0 005.636 5.636m12.728 12.728L5.636 5.636m12.728 12.728L18.364 5.636M5.636 18.364l12.728-12.728"/>
+                            </svg>
+                        </button>
+                    ` : ''}
+                    
                     <button onclick="deleteRequest(${request.id})" 
                             class="text-gray-600 hover:text-gray-900 dark:text-gray-400 dark:hover:text-gray-300 transition-colors"
                             title="Löschen">
@@ -871,17 +889,262 @@ function getTimeAgo(dateString) {
     
     const now = new Date();
     const date = new Date(dateString);
-    const diffMs = now - date;
-    const diffHours = Math.floor(diffMs / (1000 * 60 * 60));
-    const diffDays = Math.floor(diffHours / 24);
+    const diffInSeconds = Math.floor((now - date) / 1000);
     
-    if (diffDays > 0) {
-        return `vor ${diffDays} Tag${diffDays === 1 ? '' : 'en'}`;
-    } else if (diffHours > 0) {
-        return `vor ${diffHours} Stunde${diffHours === 1 ? '' : 'n'}`;
+    if (diffInSeconds < 60) return 'Gerade eben';
+    if (diffInSeconds < 3600) return `vor ${Math.floor(diffInSeconds / 60)} Min.`;
+    if (diffInSeconds < 86400) return `vor ${Math.floor(diffInSeconds / 3600)} Std.`;
+    if (diffInSeconds < 2592000) return `vor ${Math.floor(diffInSeconds / 86400)} Tagen`;
+    
+    return formatDateTime(dateString);
+}
+
+/**
+ * OTP-Code-Verwaltung
+ */
+
+// OTP-Code für genehmigte Anfrage anzeigen
+async function showOtpCode(requestId) {
+    try {
+        showLoading(true);
+        
+        const url = `${API_BASE_URL}/api/admin/requests/${requestId}/otp`;
+        const response = await fetch(url, {
+            method: 'GET',
+            headers: {
+                'Content-Type': 'application/json',
+                'X-CSRFToken': csrfToken
+            }
+        });
+        
+        if (!response.ok) {
+            throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+        }
+        
+        const data = await response.json();
+        
+        if (data.success && data.otp_code) {
+            showOtpModal(data.otp_code, data.request_id, data.expires_at, data.status);
+        } else {
+            showNotification('❌ ' + (data.error || 'OTP-Code konnte nicht abgerufen werden'), 'error');
+        }
+        
+    } catch (error) {
+        console.error('Fehler beim Abrufen des OTP-Codes:', error);
+        showNotification('❌ Fehler beim Abrufen des OTP-Codes: ' + error.message, 'error');
+    } finally {
+        showLoading(false);
+    }
+}
+
+// OTP-Modal anzeigen
+function showOtpModal(otpCode, requestId, expiresAt, status) {
+    // Bestehende Modals schließen
+    closeOtpModal();
+    
+    const modal = document.createElement('div');
+    modal.className = 'fixed inset-0 bg-black/60 dark:bg-black/80 backdrop-blur-sm z-50 flex items-center justify-center p-4';
+    modal.id = 'otp-modal';
+    
+    const expiryDate = expiresAt ? new Date(expiresAt).toLocaleString('de-DE') : 'Unbekannt';
+    const statusText = status === 'used' ? 'Bereits verwendet' : 
+                      status === 'expired' ? 'Abgelaufen' : 'Gültig';
+    const statusColor = status === 'used' ? 'text-red-600 dark:text-red-400' : 
+                       status === 'expired' ? 'text-orange-600 dark:text-orange-400' : 
+                       'text-green-600 dark:text-green-400';
+    
+    modal.innerHTML = `
+        <div class="bg-white dark:bg-slate-900 rounded-2xl shadow-2xl border border-gray-200 dark:border-slate-700 max-w-md w-full transform transition-all duration-300 scale-95 opacity-0" id="otp-modal-content">
+            <div class="p-6 border-b border-gray-200 dark:border-slate-700">
+                <div class="flex justify-between items-center">
+                    <h3 class="text-xl font-bold text-gray-900 dark:text-slate-100 flex items-center">
+                        <svg class="w-6 h-6 mr-2 text-blue-500" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 7a2 2 0 012 2m4 0a6 6 0 01-7.743 5.743L11 17H9v2H7v2H4a1 1 0 01-1-1v-3a1 1 0 011-1h2.586l6.243-6.243A6 6 0 0121 9z"/>
+                        </svg>
+                        OTP-Code
+                    </h3>
+                    <button onclick="closeOtpModal()" class="text-gray-400 hover:text-gray-600 dark:hover:text-gray-300 transition-colors">
+                        <svg class="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"/>
+                        </svg>
+                    </button>
+                </div>
+            </div>
+            <div class="p-6">
+                <div class="text-center mb-6">
+                    <div class="text-4xl font-mono font-bold text-slate-900 dark:text-slate-100 tracking-widest bg-gradient-to-r from-blue-50 to-indigo-50 dark:from-slate-800 dark:to-slate-700 rounded-lg py-6 px-6 mb-4 border-2 border-dashed border-blue-200 dark:border-slate-600">
+                        ${otpCode}
+                    </div>
+                    <p class="text-sm text-slate-500 dark:text-slate-400">6-stelliger Zugangscode für den Gast</p>
+                </div>
+                
+                <div class="space-y-3 text-sm bg-gray-50 dark:bg-slate-800 rounded-lg p-4">
+                    <div class="flex justify-between items-center">
+                        <span class="text-slate-600 dark:text-slate-400 font-medium">Status:</span>
+                        <span class="${statusColor} font-semibold flex items-center">
+                            <span class="w-2 h-2 rounded-full mr-2 ${status === 'used' ? 'bg-red-500' : status === 'expired' ? 'bg-orange-500' : 'bg-green-500'}"></span>
+                            ${statusText}
+                        </span>
+                    </div>
+                    <div class="flex justify-between items-center">
+                        <span class="text-slate-600 dark:text-slate-400 font-medium">Gültig bis:</span>
+                        <span class="text-slate-900 dark:text-slate-100 font-mono text-xs">${expiryDate}</span>
+                    </div>
+                    <div class="flex justify-between items-center">
+                        <span class="text-slate-600 dark:text-slate-400 font-medium">Anfrage-ID:</span>
+                        <span class="text-slate-900 dark:text-slate-100 font-mono">#${requestId}</span>
+                    </div>
+                </div>
+                
+                <div class="mt-6 flex space-x-3">
+                    <button onclick="copyOtpCode('${otpCode}')" 
+                            class="flex-1 px-4 py-3 bg-blue-500 dark:bg-blue-600 text-white rounded-lg hover:bg-blue-600 dark:hover:bg-blue-700 transition-colors flex items-center justify-center font-medium">
+                        <svg class="w-5 h-5 mr-2" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 16H6a2 2 0 01-2-2V6a2 2 0 012-2h8a2 2 0 012 2v2m-6 12h8a2 2 0 002-2v-8a2 2 0 00-2-2h-8a2 2 0 00-2 2v8a2 2 0 002 2z"/>
+                        </svg>
+                        Code kopieren
+                    </button>
+                    <button onclick="closeOtpModal()" 
+                            class="flex-1 px-4 py-3 bg-gray-500 dark:bg-gray-600 text-white rounded-lg hover:bg-gray-600 dark:hover:bg-gray-700 transition-colors flex items-center justify-center font-medium">
+                        <svg class="w-5 h-5 mr-2" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"/>
+                        </svg>
+                        Schließen
+                    </button>
+                </div>
+                
+                <div class="mt-4 p-3 bg-blue-50 dark:bg-blue-900/20 rounded-lg border border-blue-200 dark:border-blue-800">
+                    <p class="text-xs text-blue-700 dark:text-blue-300 flex items-start">
+                        <svg class="w-4 h-4 mr-2 mt-0.5 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/>
+                        </svg>
+                        <span>Der Gast kann diesen Code auf der Startseite eingeben, um seinen genehmigten Druckauftrag zu starten.</span>
+                    </p>
+                </div>
+            </div>
+        </div>
+    `;
+    
+    document.body.appendChild(modal);
+    
+    // Animation einblenden
+    setTimeout(() => {
+        const content = document.getElementById('otp-modal-content');
+        if (content) {
+            content.classList.remove('scale-95', 'opacity-0');
+            content.classList.add('scale-100', 'opacity-100');
+        }
+    }, 10);
+    
+    // Modal schließen bei Klick außerhalb
+    modal.addEventListener('click', function(e) {
+        if (e.target === modal) {
+            closeOtpModal();
+        }
+    });
+    
+    // ESC-Taste zum Schließen
+    const escapeHandler = function(e) {
+        if (e.key === 'Escape') {
+            closeOtpModal();
+            document.removeEventListener('keydown', escapeHandler);
+        }
+    };
+    document.addEventListener('keydown', escapeHandler);
+}
+
+// OTP-Code in Zwischenablage kopieren
+function copyOtpCode(code) {
+    if (navigator.clipboard && navigator.clipboard.writeText) {
+        navigator.clipboard.writeText(code).then(() => {
+            showNotification('📋 OTP-Code in Zwischenablage kopiert', 'success');
+        }).catch(() => {
+            fallbackCopyTextToClipboard(code);
+        });
     } else {
-        const diffMinutes = Math.floor(diffMs / (1000 * 60));
-        return `vor ${Math.max(1, diffMinutes)} Minute${diffMinutes === 1 ? '' : 'n'}`;
+        fallbackCopyTextToClipboard(code);
+    }
+}
+
+// Fallback für ältere Browser
+function fallbackCopyTextToClipboard(text) {
+    const textArea = document.createElement("textarea");
+    textArea.value = text;
+    textArea.style.top = "0";
+    textArea.style.left = "0";
+    textArea.style.position = "fixed";
+    
+    document.body.appendChild(textArea);
+    textArea.focus();
+    textArea.select();
+    
+    try {
+        const successful = document.execCommand('copy');
+        if (successful) {
+            showNotification('📋 OTP-Code in Zwischenablage kopiert', 'success');
+        } else {
+            showNotification('❌ Fehler beim Kopieren des Codes', 'error');
+        }
+    } catch (err) {
+        showNotification('❌ Fehler beim Kopieren des Codes', 'error');
+    }
+    
+    document.body.removeChild(textArea);
+}
+
+// OTP-Modal schließen
+function closeOtpModal() {
+    const modal = document.getElementById('otp-modal');
+    if (modal) {
+        const content = document.getElementById('otp-modal-content');
+        if (content) {
+            content.classList.add('scale-95', 'opacity-0');
+            content.classList.remove('scale-100', 'opacity-100');
+        }
+        
+        setTimeout(() => {
+            modal.remove();
+        }, 300);
+    }
+}
+
+// Genehmigung widerrufen
+async function revokeRequest(requestId) {
+    if (!confirm('Möchten Sie die Genehmigung dieser Anfrage wirklich widerrufen? Der OTP-Code wird ungültig.')) {
+        return;
+    }
+    
+    try {
+        showLoading(true);
+        
+        const url = `${API_BASE_URL}/api/requests/${requestId}/deny`;
+        const response = await fetch(url, {
+            method: 'POST',
+            headers: {
+                'Content-Type': 'application/json',
+                'X-CSRFToken': csrfToken
+            },
+            body: JSON.stringify({ reason: 'Genehmigung durch Administrator widerrufen' })
+        });
+        
+        if (!response.ok) {
+            throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+        }
+        
+        const data = await response.json();
+        
+        if (data.success) {
+            showNotification('✅ Genehmigung erfolgreich widerrufen', 'success');
+            loadGuestRequests(); // Tabelle aktualisieren
+        } else {
+            showNotification('❌ ' + (data.error || 'Fehler beim Widerrufen der Genehmigung'), 'error');
+        }
+        
+    } catch (error) {
+        console.error('Fehler beim Widerrufen der Genehmigung:', error);
+        showNotification('❌ Fehler beim Widerrufen der Genehmigung: ' + error.message, 'error');
+    } finally {
+        showLoading(false);
     }
 }