Fix product reservation system for demo orders

PROBLEM ANALYSIS:
- SQL script created orders bypassing Django ORM
- Django signals (post_save) didn't trigger
- No reservations were created automatically
- Found 51 orders with 102 items and 0 reservations

SOLUTION IMPLEMENTED:

1. Updated create_demo_orders command:
   - Added clear documentation about ORM usage
   - Already uses ORM (.save()) which triggers signals
   - Added informative messages about automatic reservations

2. Created fix_missing_reservations command:
   - Finds OrderItems without reservations
   - Creates missing Reservation records
   - Supports --dry-run mode for safety
   - Handles missing warehouses gracefully

3. Created SQL fix script:
   - Direct SQL approach for existing data
   - Creates reservations for all 102 items
   - Status: 'reserved'
   - Verified: All items now have reservations

4. Added verification scripts:
   - check_orders.py: Shows orders/items/reservations count
   - run_fix_reservations.py: Executes SQL fix

RESULTS:
- ✓ 102 reservations created for existing orders
- ✓ Future orders will use ORM and create reservations automatically
- ✓ System now works correctly

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

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

myproject/check_orders.py

@@ -0,0 +1,53 @@
+"""
+Проверка созданных заказов и резервов
+"""
+import os
+import django
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myproject.settings')
+django.setup()
+
+from django.db import connection
+
+with connection.cursor() as cursor:
+    cursor.execute("SET search_path TO grach")
+
+    # Считаем заказы
+    cursor.execute("SELECT COUNT(*) FROM grach.orders_order")
+    orders_count = cursor.fetchone()[0]
+    print(f"Заказов: {orders_count}")
+
+    # Считаем позиции заказов
+    cursor.execute("SELECT COUNT(*) FROM grach.orders_orderitem")
+    items_count = cursor.fetchone()[0]
+    print(f"Позиций в заказах: {items_count}")
+
+    # Считаем резервы
+    cursor.execute("SELECT COUNT(*) FROM grach.inventory_reservation")
+    reservations_count = cursor.fetchone()[0]
+    print(f"Резервов: {reservations_count}")
+
+    # Детали по заказам без резервов
+    print("\nПервые 10 позиций без резервов:")
+    cursor.execute("""
+        SELECT
+            o.order_number,
+            oi.id as item_id,
+            p.name as product_name,
+            oi.quantity,
+            COUNT(r.id) as reservations_count
+        FROM grach.orders_order o
+        JOIN grach.orders_orderitem oi ON oi.order_id = o.id
+        LEFT JOIN grach.products_product p ON p.id = oi.product_id
+        LEFT JOIN grach.inventory_reservation r ON r.order_item_id = oi.id
+        GROUP BY o.order_number, oi.id, p.name, oi.quantity
+        HAVING COUNT(r.id) = 0
+        ORDER BY o.order_number
+        LIMIT 10
+    """)
+    rows = cursor.fetchall()
+    if rows:
+        for row in rows:
+            print(f"  Заказ {row[0]}: ItemID={row[1]}, Товар=\"{row[2]}\", Кол-во={row[3]}, Резервов={row[4]}")
+    else:
+        print("  Все позиции имеют резервы!")