Improve Sales Order UX: Stock Location, Customer Filtering & Enhanced List View (#756)

* feat(sales-order): Improve UX with location display, customer filtering, and enhanced list

- Show stock location when selecting items to allocate in sales orders
- Filter inactive customers from customer selection dropdown
- Display customer name and order total in sales order list view

These changes improve the day-to-day usability for warehouse and field staff
by providing more context in key workflows without requiring extra navigation.

* Format code

lib/inventree/sales_order.dart

@@ -48,7 +48,7 @@ class InvenTreeSalesOrder extends InvenTreeOrder {
     Map<String, Map<String, dynamic>> fields = {
       "reference": {},
       "customer": {
-        "filters": {"is_customer": true},
+        "filters": {"is_customer": true, "active": true},
       },
       "customer_reference": {},
       "description": {},