feat(pos): add write-off functionality for showcase kits

Add support for writing off showcase kits by creating a write-off document with components, converting reservations, and updating statuses.

- Add `write_off_from_showcase` static method to ShowcaseManager
- Add API endpoint `/pos/api/product-kits/<int:kit_id>/write-off/`
- Add write-off button to POS terminal UI
- Implement confirmation dialog with detailed information
- Add redirect to write-off document detail page after success

The write-off process includes:
1. Creating a write-off document in draft state
2. Converting existing reservations to write-off document items
3. Marking the showcase item as dismantled
4. Setting the product kit status to discontinued (if not already)

Breaking Changes: No

myproject/pos/views.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from django.shortcuts import render, get_object_or_404
+from django.urls import reverse
 from django.contrib.auth.decorators import login_required
 from django.http import JsonResponse
 from django.views.decorators.http import require_http_methods
@@ -13,7 +14,7 @@ import json
 import logging
 
 from products.models import Product, ProductCategory, ProductKit, KitItem
-from inventory.models import Showcase, Reservation, Warehouse, Stock
+from inventory.models import Showcase, Reservation, Warehouse, Stock, ShowcaseItem
 from inventory.services import ShowcaseManager
 from inventory.signals import skip_sale_creation, reset_sale_creation
 
@@ -1536,6 +1537,88 @@ def disassemble_product_kit(request, kit_id):
         }, status=500)
 
 
+@login_required
+@require_http_methods(["POST"])
+def write_off_showcase_kit(request, kit_id):
+    """
+    Списывает витринный комплект с созданием документа списания.
+
+    Args:
+        request: HTTP запрос
+        kit_id: ID комплекта для списания
+
+    Returns:
+        JSON: {
+            'success': bool,
+            'document_id': int,
+            'document_number': str,
+            'redirect_url': str,
+            'message': str,
+            'error': str (если failed)
+        }
+    """
+    try:
+        # Получаем комплект с витриной (только временные комплекты)
+        kit = ProductKit.objects.select_related('showcase').get(id=kit_id, is_temporary=True)
+
+        # Проверяем, что комплект ещё не разобран
+        if kit.status == 'discontinued':
+            return JsonResponse({
+                'success': False,
+                'error': 'Комплект уже разобран (статус: Снят)'
+            }, status=400)
+
+        # Проверяем, что у комплекта есть привязанная витрина
+        if not kit.showcase:
+            return JsonResponse({
+                'success': False,
+                'error': 'Комплект не привязан к витрине'
+            }, status=400)
+
+        # Находим экземпляр на витрине
+        showcase_item = ShowcaseItem.objects.filter(
+            showcase=kit.showcase,
+            product_kit=kit,
+            status='available'
+        ).first()
+
+        if not showcase_item:
+            return JsonResponse({
+                'success': False,
+                'error': 'Экземпляр комплекта не найден на витрине'
+            }, status=404)
+
+        # Создаём документ списания
+        result = ShowcaseManager.write_off_from_showcase(
+            showcase_item=showcase_item,
+            reason='spoilage',
+            notes=f'Витринный букет: {kit.name}',
+            created_by=request.user
+        )
+
+        if not result['success']:
+            return JsonResponse({
+                'success': False,
+                'error': result['message']
+            }, status=400)
+
+        # Формируем URL для перенаправления
+        redirect_url = reverse('inventory:writeoff-document-detail', kwargs={'pk': result['document_id']})
+
+        return JsonResponse({
+            'success': True,
+            'document_id': result['document_id'],
+            'document_number': result['document_number'],
+            'redirect_url': redirect_url,
+            'message': result['message']
+        })
+
+    except ProductKit.DoesNotExist:
+        return JsonResponse({'success': False, 'error': 'Комплект не найден'}, status=404)
+    except Exception as e:
+        return JsonResponse({'success': False, 'error': f'Ошибка: {str(e)}'}, status=500)
+
+
 @login_required
 @require_http_methods(["POST"])
 def pos_checkout(request):