feat(guardian): Rev2 · Bus 확장 + AlarmAggregator + NotificationSubscriber

GUARDIAN-01 §Rev2 개선 4건 (파트너 앱 개발 지원):

1. BleManager · Battery/BleConnection emit 지점 추가
   - emitBatteryEvent(pct): 임계 bucket 전이 (CRITICAL<5, LOW<20, OK≥20)
   - emitConnectionEvent(state, reason): CONNECTED / DISCONNECTED / FAILED
   - CONNECTED · STATE_DISCONNECTED · GATT_ERROR · 좀비 watchdog 4 경로 wire

2. AlarmAggregator (신규 · telemetry/) — subscriber 참조 구현
   - Bus 구독 · BvEvent/PostureEvent/GaitEvent/BleConn/Battery → AlarmEvent 재발행
   - 재귀 방지 (filterNot { it is AlarmEvent })
   - Category 매핑: BV_URGENT/BV_WARN/POSTURE_TRANSITION/GAIT_STARTED/STOPPED/
     BLE_LOST/BATTERY_CRITICAL/BATTERY_LOW
   - Guardian 앱 로직 단순화 (AlarmEvent 하나만 구독하면 됨)

3. Dev-mode overlay 확장 (PiezoMonitoringView · RSSI 옆)
   - ClinicalEventBus 최근 5개 이벤트 rolling 표시
   - Type(BV/PST/GAI/BLE/BAT/ALM) + severity color + 요약
   - LaunchedEffect + mutableStateListOf · isDevMode gate

4. NotificationSubscriber (신규 · telemetry/) — in-app 소비 참조 구현
   - AlarmEvent 구독 · Android push notification 발행
   - BATTERY_CRITICAL/LOW → device_status 채널 (신규)
   - BLE_LOST → 30초 debounce · CONNECTED 시 reset
   - BV_URGENT/WARN → AppState.updateLevelFromMeasurement 직접 호출과 중복 방지 · NO-OP
   - MainActivity.onCreate 에서 start(this) 1회 호출

NotificationService 확장:
   - device_status 채널 신규 (배터리·BLE 알람용)
   - sendBatteryNotification(level, isCritical) · bucket dedup
   - sendBleLostNotification(reason) · resetBleDebounce()

의도: Guardian 앱 (동업자 · Supabase 경유) 이 in-app subscriber 와 동일 패턴으로
소비하도록 참조. 다음 단계는 GUARDIAN-02 파트너용 스키마 문서 (cloud-mvp).

app/src/main/java/com/medithings/vesiscan/services/NotificationService.kt

@@ -20,9 +20,17 @@ class NotificationService private constructor(private val context: Context) {
 
         private const val CHANNEL_ID = "bladder_urgency"
         private const val CHANNEL_NAME = "Bladder Monitoring"
+        private const val DEVICE_CHANNEL_ID = "device_status"
+        private const val BATTERY_NOTIF_ID = 1001
+        private const val BLE_NOTIF_ID = 1002
+        /** BLE 알람 최소 간격 (재연결/끊김 반복 시 스팸 방지) · ms */
+        private const val BLE_DEBOUNCE_MS = 30_000L
     }
 
     private var lastNotifiedUrgency: String? = null
+    // GUARDIAN-01 Phase D · 신규 채널 dedup key (battery bucket, BLE state).
+    @Volatile private var lastBatteryBucket: Int = -1
+    @Volatile private var lastBleAlertMs: Long = 0L
 
     init {
         createNotificationChannel()
@@ -30,16 +38,20 @@ class NotificationService private constructor(private val context: Context) {
 
     private fun createNotificationChannel() {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            val channel = NotificationChannel(
-                CHANNEL_ID,
-                CHANNEL_NAME,
-                NotificationManager.IMPORTANCE_HIGH
+            val nm = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+            val bladder = NotificationChannel(
+                CHANNEL_ID, CHANNEL_NAME, NotificationManager.IMPORTANCE_HIGH,
             ).apply {
                 description = "Bladder level urgency notifications"
                 enableVibration(true)
             }
-            val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
-            notificationManager.createNotificationChannel(channel)
+            val device = NotificationChannel(
+                DEVICE_CHANNEL_ID, "Device Status", NotificationManager.IMPORTANCE_DEFAULT,
+            ).apply {
+                description = "Battery low / BLE disconnect notifications"
+            }
+            nm.createNotificationChannel(bladder)
+            nm.createNotificationChannel(device)
         }
     }
 
@@ -70,8 +82,50 @@ class NotificationService private constructor(private val context: Context) {
         } catch (_: SecurityException) { }
     }
 
+    /** 배터리 임계 알림 · bucket 전이 시 1회만. isCritical=true → CRITICAL, false → LOW. */
+    fun sendBatteryNotification(level: Int, isCritical: Boolean) {
+        val bucket = if (isCritical) 0 else 1
+        if (bucket == lastBatteryBucket) return
+        lastBatteryBucket = bucket
+        val title = if (isCritical) "Battery Critical" else "Battery Low"
+        val body = "Device battery at $level%. Please charge soon."
+        val priority = if (isCritical) NotificationCompat.PRIORITY_HIGH else NotificationCompat.PRIORITY_DEFAULT
+        val notif = NotificationCompat.Builder(context, DEVICE_CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_launcher_foreground)
+            .setContentTitle(title)
+            .setContentText(body)
+            .setPriority(priority)
+            .setAutoCancel(true)
+            .build()
+        try { NotificationManagerCompat.from(context).notify(BATTERY_NOTIF_ID, notif) }
+        catch (_: SecurityException) { }
+    }
+
+    /** BLE 연결 해제 알림 · 30초 내 중복 억제. */
+    fun sendBleLostNotification(reason: String?) {
+        val now = System.currentTimeMillis()
+        if (now - lastBleAlertMs < BLE_DEBOUNCE_MS) return
+        lastBleAlertMs = now
+        val notif = NotificationCompat.Builder(context, DEVICE_CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_launcher_foreground)
+            .setContentTitle("Device Disconnected")
+            .setContentText(if (reason != null) "BLE connection lost · $reason" else "BLE connection lost")
+            .setPriority(NotificationCompat.PRIORITY_DEFAULT)
+            .setAutoCancel(true)
+            .build()
+        try { NotificationManagerCompat.from(context).notify(BLE_NOTIF_ID, notif) }
+        catch (_: SecurityException) { }
+    }
+
+    /** BLE 재연결 성공 시 debounce 리셋. */
+    fun resetBleDebounce() {
+        lastBleAlertMs = 0L
+    }
+
     fun cancelAll() {
         lastNotifiedUrgency = null
+        lastBatteryBucket = -1
+        lastBleAlertMs = 0L
         NotificationManagerCompat.from(context).cancelAll()
     }
 }