Remove direct reservation management from web interface

PROBLEM:
Direct deletion/creation of reservations via web interface bypassed
POS business logic, creating data inconsistencies (orphaned showcase kits,
incorrect stock calculations).

SOLUTION:
Make reservations read-only in web interface. All reservation management
now happens only through:
- POS (showcase kits)
- Orders module

CHANGES:
- Remove reservation-create and reservation-update URL routes
- Delete ReservationCreateView and ReservationUpdateView
- Remove ReservationForm (no longer needed)
- Delete reservation_form.html and reservation_update.html templates
- Update reservation_list.html to read-only view with info banner
- Add showcase and order columns to reservation list
- Clean up imports in urls.py and views/__init__.py

Reservations are now read-only for monitoring purposes only.

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

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

myproject/inventory/views/__init__.py

@@ -9,7 +9,7 @@ Inventory Views Package
 - inventory_ops.py: Инвентаризация и её строки
 - writeoff.py: Списания товара
 - transfer.py: Перемещения между складами
-- reservation.py: Резервирования товара
+- reservation.py: Резервирования товара (view-only)
 - stock.py: Справочник остатков (view-only)
 - batch.py: Справочник партий товара (view-only)
 - allocation.py: Распределение продаж по партиям (view-only)
@@ -28,7 +28,7 @@ from .inventory_ops import (
 )
 from .writeoff import WriteOffListView, WriteOffCreateView, WriteOffUpdateView, WriteOffDeleteView
 from .transfer import TransferListView, TransferBulkCreateView, TransferDetailView, TransferDeleteView, GetProductStockView
-from .reservation import ReservationListView, ReservationCreateView, ReservationUpdateView
+from .reservation import ReservationListView
 from .stock import StockListView, StockDetailView
 from .allocation import SaleBatchAllocationListView
 from .movements import StockMovementListView
@@ -60,7 +60,7 @@ __all__ = [
     # Transfer
     'TransferListView', 'TransferBulkCreateView', 'TransferDetailView', 'TransferDeleteView', 'GetProductStockView',
     # Reservation
-    'ReservationListView', 'ReservationCreateView', 'ReservationUpdateView',
+    'ReservationListView',
     # Stock
     'StockListView', 'StockDetailView',
     # StockBatch