Fix: Add _open() and path() methods to TenantAwareFileSystemStorage

Critical fix for Celery photo processing. The storage class now correctly
handles file reading operations by automatically adding tenant_id prefix
when opening files.

Problems fixed:
- Celery tasks could not open image files from storage
- PIL/Pillow couldn't locate files in tenant-specific directories
- temp file deletion was failing due to path validation

Changes:
- Added _open() method to add tenant_id prefix when opening files
- Added path() method to convert relative paths to full filesystem paths
- Updated delete() method to handle paths with or without tenant prefix
- All methods include security checks to prevent cross-tenant access

Testing:
- All 5 existing tests pass
- Verified photo processing task works end-to-end:
  * Reads temp image file from disk
  * Processes and creates all image versions
  * Saves processed files to tenant-specific directory
  * Cleans up temporary files correctly
- Files correctly stored in: media/tenants/{tenant_id}/products/{product_id}/{photo_id}/

🤖 Generated with Claude Code

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

myproject/pos/views.py

@@ -172,15 +172,24 @@ def pos_terminal(request):
     current_warehouse = get_pos_warehouse(request)
 
     if not current_warehouse:
-        # Нет активных складов - показываем ошибку
-        from django.contrib import messages
-        messages.error(request, 'Нет активных складов. Обратитесь к администратору.')
+        # Нет активных складов - информация отображается в блоке склада в шаблоне
+        # Получаем системного клиента для корректного рендеринга JSON в шаблоне
+        system_customer, _ = Customer.get_or_create_system_customer()
         context = {
             'categories_json': json.dumps([]),
             'items_json': json.dumps([]),
             'showcase_kits_json': json.dumps([]),
             'current_warehouse': None,
             'warehouses': [],
+            'system_customer': {
+                'id': system_customer.id,
+                'name': system_customer.name
+            },
+            'selected_customer': {
+                'id': system_customer.id,
+                'name': system_customer.name
+            },
+            'cart_data': json.dumps({}),
             'title': 'POS Terminal',
         }
         return render(request, 'pos/terminal.html', context)