完善生图5.0的功能

backend/internal/orchestration/settlement_test.go

@@ -102,6 +102,28 @@ func TestSettlementProcessorLeavesNonSeedanceSuccessAlone(t *testing.T) {
 	}
 }
 
+func TestSettlementProcessorRefundsUnusedSeedreamLayerReservation(t *testing.T) {
+	state := &settlementStateStub{}
+	ledger := &settlementLedgerStub{posting: billing.WalletPosting{LedgerID: "layer-settlement", CreatedAt: time.Date(2026, 8, 21, 8, 0, 0, 0, time.UTC)}}
+	advanced := jobs.Job{
+		ID: "layer-job", Provider: "seedream", ReqKey: billing.Seedream50ProModel, Capability: "image.generate", Status: jobs.StatusSucceeded,
+		RequestPayload:  json.RawMessage(`{"settings":{"creationMode":"layers","layerDecomposition":true,"size":"2K"}}`),
+		ResponsePayload: json.RawMessage(`{"status":"succeeded","raw":{"data":[{"size":"2048x2048","z_index":0},{"size":"1273x265","z_index":1}]}}`),
+		Billing:         json.RawMessage(`{"status":"charged","amountFen":612,"reservedAmountFen":612,"markupMultiplier":1.2,"settlementStatus":"pending"}`),
+		UsageContext:    json.RawMessage(`{"organizationId":"org-1","accountId":"account-1"}`),
+	}
+	processor := NewSettlementProcessor(settlementProcessorStub{job: advanced}, ledger, state, time.Now)
+	got, err := processor.Advance(context.Background(), jobs.Job{ID: "layer-job", Provider: "seedream", Status: jobs.StatusRunning})
+	if err != nil || ledger.calls != 1 || ledger.request.DeltaFen != -558 || ledger.request.Metadata["actualAmountFen"] != int64(54) {
+		t.Fatalf("job=%#v request=%#v calls=%d err=%v", got, ledger.request, ledger.calls, err)
+	}
+	var snapshot map[string]any
+	_ = json.Unmarshal(got.Billing, &snapshot)
+	if snapshot["amountFen"] != float64(54) || snapshot["settlementStatus"] != "settled" || snapshot["settlementLedgerEntryId"] != "layer-settlement" {
+		t.Fatalf("billing snapshot=%#v", snapshot)
+	}
+}
+
 func seedanceSettlementJob(response, billingJSON string) jobs.Job {
 	return jobs.Job{
 		ID: "job-1", Provider: "seedance", Capability: "video.generate", Status: jobs.StatusSucceeded,