fix: 息屏时停止电量/蓝牙/信号监听，亮屏时恢复

监听SCREEN_OFF/SCREEN_ON，息屏后注销所有广播接收器和信号监听，
亮屏后重新注册。息屏后只剩MQTT心跳，与旧版耗电一致。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/java/com/xiaoqu/watch/service/manager/SystemStateMonitor.kt

@@ -24,6 +24,7 @@ import javax.inject.Singleton
 /**
  * 系统状态监听器
  * 注册 BroadcastReceiver 监听电量、蓝牙状态变化，通过 EventBus 分发事件
+ * 息屏时自动停止监听（省电），亮屏时恢复
  *
  * 使用方式：
  * - MainActivity.onCreate 中调用 register()
@@ -55,7 +56,7 @@ class SystemStateMonitor @Inject constructor(
         }
     }
 
-    /** 广播接收器 */
+    /** 状态广播接收器（电量、蓝牙） */
     private val receiver = object : BroadcastReceiver() {
         override fun onReceive(context: Context, intent: Intent) {
             when (intent.action) {
@@ -71,10 +72,56 @@ class SystemStateMonitor @Inject constructor(
         }
     }
 
-    /** 注册广播监听 */
+    /** 屏幕开关广播接收器（控制状态监听的启停） */
+    private val screenReceiver = object : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            when (intent.action) {
+                Intent.ACTION_SCREEN_OFF -> pauseMonitoring()
+                Intent.ACTION_SCREEN_ON -> resumeMonitoring()
+            }
+        }
+    }
+
+    /** 状态监听是否活跃 */
+    private var monitoring = false
+
+    /** 注册（包含屏幕开关监听 + 启动状态监听） */
     fun register() {
         if (registered) return
 
+        // 注册屏幕开关监听（始终活跃，不受息屏影响）
+        val screenFilter = IntentFilter().apply {
+            addAction(Intent.ACTION_SCREEN_OFF)
+            addAction(Intent.ACTION_SCREEN_ON)
+        }
+        context.registerReceiver(screenReceiver, screenFilter)
+
+        // 启动状态监听
+        resumeMonitoring()
+
+        registered = true
+        Timber.d("系统状态监听: 已注册")
+    }
+
+    /** 取消注册（清理所有监听） */
+    fun unregister() {
+        if (!registered) return
+
+        pauseMonitoring()
+        try {
+            context.unregisterReceiver(screenReceiver)
+        } catch (e: Exception) {
+            Timber.w(e, "系统状态监听: 取消屏幕监听异常")
+        }
+
+        registered = false
+        Timber.d("系统状态监听: 已取消注册")
+    }
+
+    /** 启动状态监听（亮屏时调用） */
+    private fun resumeMonitoring() {
+        if (monitoring) return
+
         val filter = IntentFilter().apply {
             addAction(Intent.ACTION_BATTERY_CHANGED)
             addAction(BluetoothAdapter.ACTION_STATE_CHANGED)
@@ -83,29 +130,27 @@ class SystemStateMonitor @Inject constructor(
         }
         context.registerReceiver(receiver, filter)
 
-        // 注册信号强度监听
         val telephony = context.getSystemService(Context.TELEPHONY_SERVICE) as? TelephonyManager
         telephony?.listen(phoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS)
 
-        registered = true
-        Timber.d("系统状态监听: 已注册")
+        monitoring = true
+        Timber.d("系统状态监听: 亮屏恢复")
     }
 
-    /** 取消注册 */
-    fun unregister() {
-        if (!registered) return
+    /** 停止状态监听（息屏时调用） */
+    private fun pauseMonitoring() {
+        if (!monitoring) return
 
         try {
             context.unregisterReceiver(receiver)
         } catch (e: Exception) {
-            Timber.w(e, "系统状态监听: 取消注册异常")
+            Timber.w(e, "系统状态监听: 停止监听异常")
         }
-        // 取消信号监听
         val telephony = context.getSystemService(Context.TELEPHONY_SERVICE) as? TelephonyManager
         telephony?.listen(phoneStateListener, PhoneStateListener.LISTEN_NONE)
 
-        registered = false
-        Timber.d("系统状态监听: 已取消注册")
+        monitoring = false
+        Timber.d("系统状态监听: 息屏暂停")
     }
 
     /** 上次电量百分比（去抖用） */