fix(platform): avoid fake kafka lag

vehicle-data-platform/apps/web/src/pages/Dashboard.tsx

@@ -11,6 +11,10 @@ const statusColor: Record<string, 'green' | 'orange' | 'red' | 'grey'> = {
   error: 'red'
 };
 
+function formatLag(value?: number | null) {
+  return value == null ? '未接入' : value.toLocaleString();
+}
+
 export function Dashboard({ onOpenVehicle }: { onOpenVehicle: (vin: string) => void }) {
   const [summary, setSummary] = useState<DashboardSummary | null>(null);
   const [vehicles, setVehicles] = useState<VehicleRow[]>([]);
@@ -104,7 +108,7 @@ export function Dashboard({ onOpenVehicle }: { onOpenVehicle: (vin: string) => v
           </Col>
         </Row>
         <Card title="实时积压" bordered style={{ marginTop: 16 }}>
-          <Typography.Text>Kafka 当前消费积压：{summary?.kafkaLag ?? 0}</Typography.Text>
+          <Typography.Text>Kafka 当前消费积压：{formatLag(summary?.kafkaLag)}</Typography.Text>
         </Card>
         <Card title="车辆服务覆盖" bordered style={{ marginTop: 16 }}>
           <Form layout="horizontal" onSubmit={(values) => loadCoverage(values as Record<string, string>)} style={{ marginBottom: 12 }}>