+source +destination in payments

frontend/pshared/test/payment/payment_state_model_test.dart

@@ -64,8 +64,9 @@ void main() {
     test('isPending and isTerminal are derived from typed state', () {
       const created = Payment(
         paymentRef: 'p-1',
-        idempotencyKey: 'idem-1',
         state: 'orchestration_state_created',
+        source: null,
+        destination: null,
         orchestrationState: PaymentOrchestrationState.created,
         failureCode: null,
         failureReason: null,
@@ -76,8 +77,9 @@ void main() {
       );
       const settled = Payment(
         paymentRef: 'p-2',
-        idempotencyKey: 'idem-2',
         state: 'orchestration_state_settled',
+        source: null,
+        destination: null,
         orchestrationState: PaymentOrchestrationState.settled,
         failureCode: null,
         failureReason: null,
@@ -96,8 +98,9 @@ void main() {
     test('isFailure handles both explicit code and failed state', () {
       const withFailureCode = Payment(
         paymentRef: 'p-3',
-        idempotencyKey: 'idem-3',
         state: 'orchestration_state_executing',
+        source: null,
+        destination: null,
         orchestrationState: PaymentOrchestrationState.executing,
         failureCode: 'failure_ledger',
         failureReason: 'ledger failed',
@@ -108,8 +111,9 @@ void main() {
       );
       const failedState = Payment(
         paymentRef: 'p-4',
-        idempotencyKey: 'idem-4',
         state: 'orchestration_state_failed',
+        source: null,
+        destination: null,
         orchestrationState: PaymentOrchestrationState.failed,
         failureCode: null,
         failureReason: null,