修复仲裁退款并新增免押额度

backend/internal/modules/order/repository_test.go

@@ -123,6 +123,23 @@ func TestCalculateCheckoutSettlementAddsDepositCompensation(t *testing.T) {
 	}
 }
 
+func TestCalculateDepositWaiverUsesSharedRemainingQuota(t *testing.T) {
+	paid, waived := calculateDepositWaiver(500, 300, 0)
+	if paid != 200 || waived != 300 {
+		t.Fatalf("paid = %.1f, waived = %.1f, want 200.0, 300.0", paid, waived)
+	}
+
+	paid, waived = calculateDepositWaiver(500, 300, 200)
+	if paid != 400 || waived != 100 {
+		t.Fatalf("paid = %.1f, waived = %.1f, want 400.0, 100.0", paid, waived)
+	}
+
+	paid, waived = calculateDepositWaiver(500, 300, 300)
+	if paid != 500 || waived != 0 {
+		t.Fatalf("paid = %.1f, waived = %.1f, want 500.0, 0.0", paid, waived)
+	}
+}
+
 func TestArchiveListingAfterCheckoutMovesListingOffline(t *testing.T) {
 	// This test is purely for contract documentation; no behavior is tested yet.
 	// When implementing auto-archive behavior: