fix: Улучшения системы ценообразования комплектов

Исправлены 4 проблемы:
1. Расчёт цены первого товара - улучшена валидация в getProductPrice и calculateFinalPrice
2. Отображение actual_price в Select2 вместо обычной цены
3. Количество по умолчанию = 1 для новых форм компонентов
4. Auto-select текста при клике на поле количества для удобства редактирования

Изменённые файлы:
- products/forms.py: добавлен __init__ в KitItemForm для quantity.initial = 1
- products/templates/includes/select2-product-init.html: обновлена formatSelectResult
- products/templates/productkit_create.html: добавлен focus handler для auto-select
- products/templates/productkit_edit.html: добавлен focus handler для auto-select

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

test_writeoff_validation.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python
+"""
+Test script to verify WriteOff form validation prevents over-listing.
+This tests that WriteOffForm.clean() prevents creating WriteOff with quantity > batch.quantity
+"""
+
+import os
+import sys
+import django
+
+# Setup Django
+sys.path.insert(0, 'myproject')
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myproject.settings')
+django.setup()
+
+from inventory.forms import WriteOffForm
+from inventory.models import WriteOff, StockBatch, Warehouse, Product
+from django.core.exceptions import ValidationError
+
+print("=" * 70)
+print("Testing WriteOff Validation")
+print("=" * 70)
+
+# Create test data
+warehouse = Warehouse.objects.filter(is_active=True).first()
+if not warehouse:
+    print("ERROR: No active warehouse found. Please create one first.")
+    sys.exit(1)
+
+product = Product.objects.filter(tenant=warehouse.tenant).first()
+if not product:
+    print("ERROR: No product found. Please create one first.")
+    sys.exit(1)
+
+# Create a batch with 2 items
+batch = StockBatch.objects.create(
+    product=product,
+    warehouse=warehouse,
+    quantity=2,
+    cost_price=100.0,
+    is_active=True
+)
+
+print(f"\n✓ Created StockBatch with quantity=2")
+print(f"  Product: {product.name}")
+print(f"  Warehouse: {warehouse.name}")
+print(f"  Batch ID: {batch.id}")
+
+# Test 1: Valid WriteOff (quantity = batch.quantity)
+print("\n" + "=" * 70)
+print("Test 1: Valid WriteOff with quantity=2 (equal to batch quantity)")
+print("=" * 70)
+
+form_data = {
+    'batch': batch.id,
+    'quantity': 2,
+    'reason': 'damage',
+    'document_number': 'DOC001',
+    'notes': 'Test valid writeoff'
+}
+
+form = WriteOffForm(data=form_data)
+if form.is_valid():
+    print("✓ PASS: Form is valid (quantity <= batch.quantity)")
+else:
+    print(f"✗ FAIL: Form should be valid but has errors: {form.errors}")
+
+# Test 2: Invalid WriteOff (quantity > batch.quantity)
+print("\n" + "=" * 70)
+print("Test 2: Invalid WriteOff with quantity=3 (exceeds batch quantity=2)")
+print("=" * 70)
+
+form_data = {
+    'batch': batch.id,
+    'quantity': 3,
+    'reason': 'damage',
+    'document_number': 'DOC002',
+    'notes': 'Test invalid writeoff - should be rejected'
+}
+
+form = WriteOffForm(data=form_data)
+if not form.is_valid():
+    print("✓ PASS: Form validation correctly rejects over-listing")
+    for field, errors in form.errors.items():
+        for error in errors:
+            print(f"  Error: {error}")
+else:
+    print("✗ FAIL: Form should reject quantity > batch.quantity")
+
+# Test 3: Invalid WriteOff (quantity = 0)
+print("\n" + "=" * 70)
+print("Test 3: Invalid WriteOff with quantity=0 (should be > 0)")
+print("=" * 70)
+
+form_data = {
+    'batch': batch.id,
+    'quantity': 0,
+    'reason': 'damage',
+    'document_number': 'DOC003',
+    'notes': 'Test zero quantity'
+}
+
+form = WriteOffForm(data=form_data)
+if not form.is_valid():
+    print("✓ PASS: Form validation correctly rejects zero quantity")
+    for field, errors in form.errors.items():
+        for error in errors:
+            print(f"  Error: {error}")
+else:
+    print("✗ FAIL: Form should reject quantity <= 0")
+
+# Cleanup
+batch.delete()
+print("\n" + "=" * 70)
+print("Test completed successfully!")
+print("=" * 70)