refactor: подготовка к стандартизации Transfer моделей

Текущее состояние перед рефакторингом Transfer → TransferDocument.
Все изменения с последнего коммита по улучшению системы поступлений.

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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

myproject/inventory/admin.py

@@ -5,7 +5,7 @@ from django.db.models import Sum
 from decimal import Decimal
 
 from inventory.models import (
-    Warehouse, StockBatch, Incoming, IncomingBatch, Sale, WriteOff, Transfer,
+    Warehouse, StockBatch, Sale, WriteOff, Transfer,
     Inventory, InventoryLine, Reservation, Stock, StockMovement,
     SaleBatchAllocation, Showcase, WriteOffDocument, WriteOffDocumentItem,
     IncomingDocument, IncomingDocumentItem, Transformation, TransformationInput,