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/fix_reservations.sql

@@ -0,0 +1,59 @@
+-- Создание резервов для всех позиций заказов без резервов
+SET search_path TO grach;
+
+-- Проверяем наличие активного склада
+DO $$
+DECLARE
+    warehouse_id_val INT;
+    created_count INT := 0;
+BEGIN
+    -- Получаем ID активного склада (если есть)
+    SELECT id INTO warehouse_id_val
+    FROM grach.inventory_warehouse
+    WHERE is_active = true
+    LIMIT 1;
+
+    IF warehouse_id_val IS NULL THEN
+        RAISE NOTICE 'WARNING: Нет активного склада, резервы будут созданы без склада';
+    ELSE
+        RAISE NOTICE 'Используем склад ID: %', warehouse_id_val;
+    END IF;
+
+    -- Создаем резервы для всех позиций без резервов
+    INSERT INTO grach.inventory_reservation (
+        order_item_id,
+        product_id,
+        warehouse_id,
+        quantity,
+        status,
+        reserved_at,
+        released_at,
+        converted_at
+    )
+    SELECT
+        oi.id,
+        COALESCE(oi.product_id, oi.product_kit_id),
+        warehouse_id_val,
+        oi.quantity,
+        'reserved',
+        CURRENT_TIMESTAMP,
+        NULL,
+        NULL
+    FROM grach.orders_orderitem oi
+    LEFT JOIN grach.inventory_reservation r ON r.order_item_id = oi.id
+    WHERE r.id IS NULL  -- Только позиции без резервов
+      AND (oi.product_id IS NOT NULL OR oi.product_kit_id IS NOT NULL)  -- Есть товар
+    ON CONFLICT DO NOTHING;
+
+    GET DIAGNOSTICS created_count = ROW_COUNT;
+
+    RAISE NOTICE 'Создано резервов: %', created_count;
+END $$;
+
+-- Проверяем результат
+SELECT
+    COUNT(*) as total_items,
+    COUNT(r.id) as items_with_reservations,
+    COUNT(*) - COUNT(r.id) as items_without_reservations
+FROM grach.orders_orderitem oi
+LEFT JOIN grach.inventory_reservation r ON r.order_item_id = oi.id;