feat: add Purchase Team root node as default fixture on install

Mirrors the Sales Person/Sales Team fixture so fresh installs get a
root "Purchase Team" group node for the Purchase Person tree.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

erpnext/setup/setup_wizard/operations/install_fixtures.py

@@ -248,6 +248,13 @@ def get_preset_records(country=None):
 			"is_group": 1,
 			"parent_sales_person": "",
 		},
+		# Purchase Person
+		{
+			"doctype": "Purchase Person",
+			"purchase_person_name": _("Purchase Team"),
+			"is_group": 1,
+			"parent_purchase_person": "",
+		},
 		# Mode of Payment
 		{
 			"doctype": "Mode of Payment",