fix: scope Opportunity party validation to Customer only

validate_party_frozen_disabled only enforces Customer/Supplier/Employee,
so passing opportunity_from straight through silently no-op'd for Lead
and Prospect. Made the Customer-only scope explicit instead of relying
on that implicit fallthrough.

Lead.disabled is not enforced anywhere else in the codebase (lead_query,
the picker used for this same field, only filters status/docstatus), so
deliberately not extending validation to Lead-sourced Opportunities.

(cherry picked from commit 8c0a945417)

erpnext/crm/doctype/opportunity/opportunity.py

@@ -351,7 +351,8 @@ class Opportunity(TransactionBase, CRMNote):
 			return True
 
 	def validate_party(self) -> None:
-		validate_party_frozen_disabled(self.company, self.opportunity_from, self.party_name)
+		if self.opportunity_from == "Customer":
+			validate_party_frozen_disabled(self.company, "Customer", self.party_name)
 
 	def validate_cust_name(self):
 		if self.party_name:

erpnext/crm/doctype/opportunity/test_opportunity.py

@@ -80,6 +80,15 @@ class TestOpportunity(ERPNextTestSuite):
 		frappe.db.set_value("Customer", "_Test Customer", "disabled", 0)
 		make_opportunity(with_items=0)
 
+	def test_disabled_lead_not_blocked(self):
+		# Lead.disabled isn't enforced anywhere else (e.g. the Lead picker query only
+		# excludes Converted leads), so it shouldn't block Opportunity creation either.
+		lead_doc = make_lead()
+		frappe.db.set_value("Lead", lead_doc.name, "disabled", 1)
+
+		opp_doc = make_opportunity(opportunity_from="Lead", lead=lead_doc.name)
+		self.assertEqual(opp_doc.party_name, lead_doc.name)
+
 	def test_carry_forward_of_email_and_comments(self):
 		frappe.db.set_single_value("CRM Settings", "carry_forward_communication_and_comments", 1)
 		lead_doc = make_lead()