Fix cart lock validation and error handling improvements

## 1. Add cart lock validation to sell_from_showcase()
- Prevent selling showcase kits locked in another cashier's cart
- Check cart_lock_expires_at before allowing direct sales
- Return clear error message with lock holder's name and time remaining
- File: inventory/services/showcase_manager.py

## 2. Improve error handling in POS create_temp_kit_to_showcase()
- Add detailed logging for all error types (JSON, validation, generic)
- Provide user-friendly error messages instead of generic 500
- Log full context (kit name, showcase ID, items, user) for debugging
- Categorize errors: stock issues, integrity, locks, not found
- File: pos/views.py

## 3. Fix critical bug in create_temporary_kit()
- Replace non-existent is_active field with status='active'
- Affects 3 locations: kit creation, product lookup, kit duplication
- This was causing 500 errors when creating temporary kits from order edit
- File: products/services/kit_service.py

## 4. Improve error handling in create_temporary_kit_api()
- Add comprehensive logging for order creation endpoint
- Provide specific error messages for common failure scenarios
- Help diagnose issues when creating kits from order editing UI
- File: products/views/api_views.py

These changes complete the Soft Lock system and fix the 500 error issue.

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

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

myproject/products/services/kit_service.py

@@ -57,7 +57,7 @@ def create_temporary_kit(
             name=name.strip(),
             description=description.strip() if description else '',
             is_temporary=True,
-            is_active=True,
+            status='active',
             order=order,
             price_adjustment_type='none'
         )
@@ -72,7 +72,7 @@ def create_temporary_kit(
                 continue
 
             try:
-                product = Product.objects.get(pk=product_id, is_active=True)
+                product = Product.objects.get(pk=product_id, status='active')
                 KitItem.objects.create(
                     kit=kit,
                     product=product,
@@ -135,7 +135,7 @@ def duplicate_kit(kit: ProductKit, new_name: Optional[str] = None) -> ProductKit
             price_adjustment_value=kit.price_adjustment_value,
             sale_price=kit.sale_price,
             is_temporary=False,  # Копия всегда постоянная
-            is_active=kit.is_active
+            status=kit.status
         )
 
         # Копируем категории