feat: Add customer prefill from URL parameter in order creation

- Modified order_create view to read customer from GET parameter
- Pass preselected_customer to template context
- Template renders select with preselected option for Select2
- Fixed draft creation timing with callback after Select2 initialization
- Auto-create draft when customer is preselected from URL
- Graceful handling if customer not found or invalid ID

myproject/orders/views.py

@@ -108,7 +108,19 @@ def order_create(request):
         else:
             messages.error(request, 'Пожалуйста, исправьте ошибки в форме.')
     else:
-        form = OrderForm()
+        # Предзаполнение клиента из GET параметра
+        initial_data = {}
+        preselected_customer = None
+        customer_id = request.GET.get('customer')
+        if customer_id:
+            try:
+                from customers.models import Customer
+                preselected_customer = Customer.objects.get(pk=customer_id)
+                initial_data['customer'] = preselected_customer.pk
+            except (Customer.DoesNotExist, ValueError):
+                pass
+
+        form = OrderForm(initial=initial_data)
         formset = OrderItemFormSet()
         payment_formset = PaymentFormSet()
 
@@ -116,6 +128,7 @@ def order_create(request):
         'form': form,
         'formset': formset,
         'payment_formset': payment_formset,
+        'preselected_customer': preselected_customer,
         'title': 'Создание заказа',
         'button_text': 'Создать заказ',
     }