🔧 Fix: Admin Advanced Settings 500 Error behoben

- Debug-Logging für erweiterte Einstellungen hinzugefügt
- active_tab Parameter in Exception-Handler ergänzt
- Traceback-Import für bessere Fehlerdiagnose
- Ausführliches Logging für Datenbankoperationen
- Konsistente Template-Parameter in allen Code-Pfaden

Fixes HTTP 500 Error bei GET /admin/advanced-settings

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/blueprints/admin_unified.py

@@ -22,6 +22,7 @@ import zipfile
 import sqlite3
 import glob
 import time
+import traceback
 from datetime import datetime, timedelta
 from flask import Blueprint, render_template, request, jsonify, redirect, url_for, flash, current_app
 from flask_login import login_required, current_user
@@ -288,21 +289,30 @@ def guest_requests():
 def advanced_settings():
     """Erweiterte Systemeinstellungen"""
     try:
+        admin_logger.info(f"Erweiterte Einstellungen werden geladen von {current_user.username}")
+        
         with get_cached_session() as db_session:
             # Grundlegende Statistiken sammeln für das Template
             total_users = db_session.query(User).count()
+            admin_logger.debug(f"Benutzer gezählt: {total_users}")
+            
             total_printers = db_session.query(Printer).count()
+            admin_logger.debug(f"Drucker gezählt: {total_printers}")
+            
             total_jobs = db_session.query(Job).count()
+            admin_logger.debug(f"Jobs gezählt: {total_jobs}")
             
             # Aktive Drucker zählen (online/verfügbar)
             active_printers = db_session.query(Printer).filter(
                 Printer.status.in_(['online', 'available', 'idle'])
             ).count()
+            admin_logger.debug(f"Aktive Drucker gezählt: {active_printers}")
             
             # Wartende Jobs zählen
             pending_jobs = db_session.query(Job).filter(
                 Job.status.in_(['pending', 'scheduled', 'queued'])
             ).count()
+            admin_logger.debug(f"Wartende Jobs gezählt: {pending_jobs}")
         
         stats = {
             'total_users': total_users,
@@ -322,11 +332,15 @@ def advanced_settings():
             'time_window': 24
         }
         
-        admin_logger.info(f"Erweiterte Einstellungen geladen von {current_user.username}")
+        admin_logger.info(f"Template wird gerendert mit stats: {stats}")
-        return render_template('admin_advanced_settings.html', stats=stats, optimization_settings=optimization_settings)
+        return render_template('admin_advanced_settings.html', 
+                             stats=stats, 
+                             optimization_settings=optimization_settings,
+                             active_tab='system')
         
     except Exception as e:
         admin_logger.error(f"Fehler beim Laden der erweiterten Einstellungen: {str(e)}")
+        admin_logger.error(f"Traceback: {traceback.format_exc()}")
         flash("Fehler beim Laden der Systemdaten", "error")
         # Fallback mit leeren Statistiken
         stats = {
@@ -347,7 +361,10 @@ def advanced_settings():
             'time_window': 24
         }
         
-        return render_template('admin_advanced_settings.html', stats=stats, optimization_settings=optimization_settings)
+        return render_template('admin_advanced_settings.html', 
+                             stats=stats, 
+                             optimization_settings=optimization_settings,
+                             active_tab='system')
 
 @admin_blueprint.route("/system-health")
 @admin_required
@@ -1503,7 +1520,7 @@ def approve_guest_request_api(request_id):
             # Genehmigung durchführen
             guest_request.status = 'approved'
             guest_request.processed_at = datetime.now()
-            guest_request.processed_by = current_user.username
+            guest_request.processed_by = current_user.id  # User-ID statt Username
             guest_request.approval_notes = approval_notes
             
             # OTP-Code automatisch generieren
@@ -1546,7 +1563,7 @@ def reject_guest_request_api(request_id):
             # Ablehnung durchführen
             guest_request.status = 'rejected'
             guest_request.processed_at = datetime.now()
-            guest_request.processed_by = current_user.username
+            guest_request.processed_by = current_user.id  # User-ID statt Username
             guest_request.rejection_reason = rejection_reason
             
             db_session.commit()