fix(stock): keep item-search ordering for Quality Inspection on Postgres (#56372)

The Quality Inspection item link search builds a distinct, paginated
get_query with order_by="items.item_code". frappe's db_query silently drops
the ORDER BY for a distinct query on Postgres, so with offset/limit the
results come back in a different order AND a different page slice than MariaDB.

Append the ordering to the built query instead of passing order_by: item_code
is already in the DISTINCT select list, so ORDER BY on it is valid under
DISTINCT on Postgres, and it now applies before LIMIT on both engines. MariaDB
output is unchanged (it was already ordered by item_code). The items child
field is guarded for None so a doctype without it degrades gracefully rather
than raising AttributeError.

erpnext/stock/doctype/quality_inspection/quality_inspection.py

@@ -413,16 +413,22 @@ def item_query(doctype: Any, txt: str | None, searchfield: Any, start: int, page
 				]
 			)
 
-		return frappe.get_query(
+		query = frappe.get_query(
 			reference_doctype,
 			fields=["items.item_code, items.item_name"],
 			filters=my_filters,
 			offset=start,
 			limit=page_len,
-			order_by="items.item_code",
 			ignore_permissions=False,
 			distinct=True,
-		).run()
+		)
+		# frappe's db_query drops ORDER BY for a distinct query on Postgres, which (with offset/limit)
+		# changes both the order and the page contents vs MariaDB. Appending the order to the built
+		# query instead keeps it -- item_code is in the DISTINCT select, so it is valid on Postgres.
+		items_field = frappe.get_meta(reference_doctype).get_field("items")
+		if items_field:
+			query = query.orderby(frappe.qb.DocType(items_field.options).item_code)
+		return query.run()
 
 
 @frappe.whitelist()