feat(t227): query ERP directly from Go

backend-api/internal/usecase/freight_service.go

@@ -672,7 +672,7 @@ func daysInclusive(start, end time.Time) int {
 func freightSourceErrorCode(err error) string {
 	switch {
 	case errors.Is(err, domain.ErrFreightSourceNotConfigured):
-		return "ERP_CONNECTOR_NOT_CONFIGURED"
+		return "ERP_NOT_CONFIGURED"
 	case errors.Is(err, domain.ErrFreightSourceSessionNeeded):
 		return "ERP_SESSION_REQUIRED"
 	case errors.Is(err, domain.ErrFreightSourceNotFound):
@@ -680,7 +680,7 @@ func freightSourceErrorCode(err error) string {
 	case errors.Is(err, domain.ErrFreightSourceProtocol):
 		return "ERP_RESPONSE_INVALID"
 	default:
-		return "ERP_CONNECTOR_UNAVAILABLE"
+		return "ERP_UNAVAILABLE"
 	}
 }
 

backend-api/internal/usecase/freight_service_test.go

@@ -55,6 +55,24 @@ func TestFreightNormalizationRejectsConflictingIdentityAndInvalidTime(
 	}
 }
 
+func TestFreightSourceErrorCodesAreSourceNeutral(t *testing.T) {
+	cases := []struct {
+		err  error
+		want string
+	}{
+		{domain.ErrFreightSourceNotConfigured, "ERP_NOT_CONFIGURED"},
+		{domain.ErrFreightSourceSessionNeeded, "ERP_SESSION_REQUIRED"},
+		{domain.ErrFreightSourceNotFound, "ERP_FREIGHT_NOT_FOUND"},
+		{domain.ErrFreightSourceProtocol, "ERP_RESPONSE_INVALID"},
+		{errors.New("temporary source failure"), "ERP_UNAVAILABLE"},
+	}
+	for _, testCase := range cases {
+		if got := freightSourceErrorCode(testCase.err); got != testCase.want {
+			t.Fatalf("freightSourceErrorCode(%v) = %q, want %q", testCase.err, got, testCase.want)
+		}
+	}
+}
+
 func TestFreightDateQuerySplitsIntoSevenDayWindows(t *testing.T) {
 	source := &recordingDateSource{}
 	service := &FreightService{source: source}