fix(scale): 修复子设备断线后重连慢及连接状态竞态问题

- onDeviceDisconnected 时同步清除 UDP 缓存，使子设备 5s 内即可重连，不再等待指数退避
- ScaleWebSocketServer 用 connectionCount 计数器替代 connections.isNullOrEmpty()，消除 onClose 竞态导致子设备 UI 状态不更新的问题

app/src/main/java/com/shuwei/dish/match/scale/ScaleServiceManager.kt

@@ -156,7 +156,11 @@ object ScaleServiceManager {
         val client = ScaleWebSocketClient().also {
             it.onScaleData = { data -> aggregator?.onRemoteScaleData(data) }
             it.onScaleEvent = { event -> _onScaleEvent?.invoke(event) }
-            it.onDeviceDisconnected = { remoteId -> aggregator?.removeDevice(remoteId) }
+            it.onDeviceDisconnected = { remoteId ->
+                aggregator?.removeDevice(remoteId)
+                // 清除 UDP 缓存，确保子设备下次广播时能重新触发 onDeviceFound，立即重连而非等待指数退避
+                udpReceiver?.removeDevice(remoteId)
+            }
             it.onDeviceConnected = { remoteId ->
                 // 子设备连接成功时，从 Room 读取全量配置并单独推送给该设备
                 CoroutineScope(Dispatchers.IO).launch {

app/src/main/java/com/shuwei/dish/match/scale/ScaleWebSocketServer.kt

@@ -117,7 +117,11 @@ class ScaleWebSocketServer(private val deviceId: String, private val context: Co
     private inner class InternalServer(port: Int) :
         WebSocketServer(InetSocketAddress(port)) {
 
+        /** 当前活跃连接计数，用于替代 connections.isNullOrEmpty() 避免竞态 */
+        private var connectionCount = 0
+
         override fun onOpen(conn: WebSocket, handshake: ClientHandshake) {
+            connectionCount++
             Log.d(TAG, "主设备已连接: ${conn.remoteSocketAddress}")
             onConnectionChanged?.invoke(true)
             // 新客户端连接后，立即推送所有秤的最新数据
@@ -132,8 +136,9 @@ class ScaleWebSocketServer(private val deviceId: String, private val context: Co
 
         override fun onClose(conn: WebSocket, code: Int, reason: String, remote: Boolean) {
             Log.d(TAG, "主设备已断开: ${conn.remoteSocketAddress}, reason=$reason")
-            // 若已无任何连接，通知子设备 UI 更新为未连接状态
+            // 用计数器判断是否还有活跃连接，避免依赖 connections 集合的移除时机导致竞态
-            if (server?.connections.isNullOrEmpty()) {
+            if (--connectionCount <= 0) {
+                connectionCount = 0
                 onConnectionChanged?.invoke(false)
             }
         }