feat(platform): expose active connection capacity

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

@@ -188,8 +188,8 @@ export function Quality({
       </div>
       <Row gutter={16}>
         <Col span={6}><Card bordered title="Kafka Lag">{formatLag(health?.kafkaLag)}</Card></Col>
+        <Col span={6}><Card bordered title="活跃连接">{formatLag(health?.activeConnections)}</Card></Col>
         <Col span={6}><Card bordered title="Redis 在线 Key">{formatLag(health?.redisOnlineKeys)}</Card></Col>
-        <Col span={6}><Card bordered title="BFF 请求超时">{formatRequestTimeout(health)}</Card></Col>
         <Col span={6}>
           <Card bordered title="存储读取">
             <Tag color={statusColor[storageReadStatus(health)] ?? 'grey'}>