Add configurable default for PO line item merging (#12472)

* Add configurable default for PO line item merging

Introduce PURCHASEORDER_MERGE_LINE_ITEMS global setting to control the
default state of the merge_items option when creating purchase order lines.

Fixes #10947

* Apply ruff and biome formatting for CI

src/frontend/src/components/wizards/OrderPartsWizard.tsx

@@ -32,6 +32,7 @@ import { usePurchaseOrderFields } from '../../forms/PurchaseOrderForms';
 import { useCreateApiFormModal } from '../../hooks/UseForm';
 import { useInstance } from '../../hooks/UseInstance';
 import useWizard from '../../hooks/UseWizard';
+import { useGlobalSettingsState } from '../../states/SettingsStates';
 import RemoveRowButton from '../buttons/RemoveRowButton';
 import { StandaloneField } from '../forms/StandaloneField';
 import Expand from '../items/Expand';
@@ -195,6 +196,7 @@ function SelectPartsStep({
   const [selectedRecord, setSelectedRecord] = useState<PartOrderRecord | null>(
     null
   );
+  const globalSettings = useGlobalSettingsState();
 
   const purchaseOrderFields = usePurchaseOrderFields({
     supplierId: selectedRecord?.supplier_part?.supplier
@@ -240,9 +242,11 @@ function SelectPartsStep({
       },
       purchase_price: {},
       purchase_price_currency: {},
-      merge_items: {}
+      merge_items: {
+        default: globalSettings.isSet('PURCHASEORDER_MERGE_LINE_ITEMS', true)
+      }
     };
-  }, [selectedRecord]);
+  }, [selectedRecord, globalSettings]);
 
   const addToOrder = useCreateApiFormModal({
     url: apiUrl(ApiEndpoints.purchase_order_line_list),

src/frontend/src/forms/PurchaseOrderForms.tsx

@@ -220,7 +220,9 @@ export function usePurchaseOrderLineItemFields({
     }
 
     if (create) {
-      fields['merge_items'] = {};
+      fields['merge_items'] = {
+        default: globalSettings.isSet('PURCHASEORDER_MERGE_LINE_ITEMS', true)
+      };
     }
 
     return fields;