feat: Entferne die alte Drucker-API-Route und aktualisiere die Frontend-Fehlerbehandlung für Druckeroperationen

backend/app/app.py

@@ -1100,68 +1100,7 @@ def delete_user(user_id):
         flash(f"Fehler beim Löschen des Benutzers: {str(e)}", "error")
         return redirect(url_for('admin_page', tab='users'))
 
-@app.route("/api/printers", methods=["POST"])
-@login_required
-def create_printer():
-    """Create a new printer (admin only)"""
-    if not current_user.is_admin:
-        flash("Sie haben keine Berechtigung, um neue Drucker anzulegen.", "error")
-        return redirect(url_for('admin_page', tab='printers'))
-        
-    db_session = get_db_session()
-    try:
-        # Statt JSON-Daten die Formulardaten aus dem POST-Request holen
-        name = request.form.get('name')
-        model = request.form.get('model')
-        location = request.form.get('location')
-        mac_address = request.form.get('mac_address')
-        plug_ip = request.form.get('plug_ip')
-        plug_username = request.form.get('plug_username')
-        plug_password = request.form.get('plug_password')
-        
-        # Check required fields
-        if not name or not mac_address:
-            db_session.close()
-            flash("Name und MAC-Adresse sind Pflichtfelder.", "error")
-            return redirect(url_for('admin_page', tab='printers'))
-                
-        # Check if printer with same MAC already exists
-        existing_printer = db_session.query(Printer).filter(
-            Printer.mac_address == mac_address
-        ).first()
-        
-        if existing_printer:
-            db_session.close()
-            flash("Ein Drucker mit dieser MAC-Adresse existiert bereits.", "error")
-            return redirect(url_for('admin_page', tab='printers'))
-            
-        # Create new printer
-        new_printer = Printer(
-            name=name,
-            model=model or "",
-            location=location or "",
-            mac_address=mac_address,
-            plug_ip=plug_ip or "",
-            plug_username=plug_username or "",
-            plug_password=plug_password or "",
-            active=True
-        )
-        
-        db_session.add(new_printer)
-        db_session.commit()
-        
-        printer_id = new_printer.id
-        
-        db_session.close()
-        app_logger.info(f"New printer created: {new_printer.name} (ID: {printer_id})")
-        flash(f"Drucker {name} wurde erfolgreich angelegt.", "success")
-        return redirect(url_for('admin_page', tab='printers'))
-    except Exception as e:
-        db_session.rollback()
-        db_session.close()
-        app_logger.error(f"Error creating printer: {str(e)}")
-        flash(f"Fehler beim Anlegen des Druckers: {str(e)}", "error")
-        return redirect(url_for('admin_page', tab='printers'))
+# Diese Route wurde entfernt - verwende stattdessen /api/printers/add für JSON-API
 
 @app.route("/api/printers/<int:printer_id>", methods=["DELETE"])
 @login_required