feat: 接入真实信号强度显示（之前写死满格）

- AppEvent 新增 SignalChanged 事件
- SystemStateMonitor 注册 PhoneStateListener 监听信号强度
- HomeFragment 接收事件更新 StatusBar 信号条（0-4级）

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

app/src/main/java/com/xiaoqu/watch/event/AppEvent.kt

@@ -23,6 +23,8 @@ sealed class AppEvent {
     data class BluetoothStateChanged(val isOn: Boolean) : AppEvent()
     data class BluetoothDeviceConnected(val deviceName: String) : AppEvent()
     data class BluetoothDeviceDisconnected(val deviceName: String) : AppEvent()
+    /** 信号强度变化 (level: 0-4) */
+    data class SignalChanged(val level: Int) : AppEvent()
 
     // 消息通知
     /** 新任务到达（携带任务 ID 列表，横幅+红点用） */

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

@@ -7,6 +7,9 @@ import android.content.Context
 import android.content.Intent
 import android.content.IntentFilter
 import android.os.BatteryManager
+import android.telephony.PhoneStateListener
+import android.telephony.SignalStrength
+import android.telephony.TelephonyManager
 import com.xiaoqu.watch.event.AppEvent
 import com.xiaoqu.watch.event.EventBus
 import dagger.hilt.android.qualifiers.ApplicationContext
@@ -37,6 +40,16 @@ class SystemStateMonitor @Inject constructor(
     /** 是否已注册 */
     private var registered = false
 
+    /** 信号强度监听器 */
+    private val phoneStateListener = object : PhoneStateListener() {
+        @Suppress("DEPRECATION")
+        override fun onSignalStrengthsChanged(signalStrength: SignalStrength) {
+            // 将信号强度转换为 0-4 级
+            val level = signalStrength.level  // API 23+ 返回 0-4
+            emitEvent(AppEvent.SignalChanged(level))
+        }
+    }
+
     /** 广播接收器 */
     private val receiver = object : BroadcastReceiver() {
         override fun onReceive(context: Context, intent: Intent) {
@@ -64,6 +77,11 @@ class SystemStateMonitor @Inject constructor(
             addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED)
         }
         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")
     }
@@ -77,6 +95,10 @@ class SystemStateMonitor @Inject constructor(
         } catch (e: Exception) {
             Timber.w(e, "系统状态监听: 取消注册异常")
         }
+        // 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")
     }

app/src/main/java/com/xiaoqu/watch/ui/home/HomeFragment.kt

@@ -533,6 +533,10 @@ class HomeFragment : BaseFragment<FragmentHomeBinding>() {
                     is AppEvent.BluetoothStateChanged -> {
                         statusBar.updateBluetooth(event.isOn)
                     }
+                    // 信号强度变化
+                    is AppEvent.SignalChanged -> {
+                        statusBar.updateSignal(event.level)
+                    }
                     // 蓝牙设备连接/断开 → 更新设置页
                     is AppEvent.BluetoothDeviceConnected -> {
                         updateConfigBluetooth(true)