feat(worker): add device registration_id cleanup worker

Add DeviceCleanupWorker to periodically clean up stale device tokens that haven't
been used within the retention period. This prevents accumulation of invalid
registration_ids and maintains data hygiene.

- New DeviceCleanupConfig with enabled, retention_days (3), and interval_minutes (360)
- New repository methods DeleteStaleDevices and DeleteOldestActiveDevice
- Updated RegisterDevice to evict oldest active device when reaching limit
- Reduced MaxDevicesPerUser from 10 to 3 per user
- Worker integrated into app startup/shutdown lifecycle

internal/service/push_service.go

@@ -28,7 +28,7 @@ const (
 	// PushQueueSize 推送队列大小
 	PushQueueSize = 1000
 	// MaxDevicesPerUser 每个用户最大设备数
-	MaxDevicesPerUser = 10
+	MaxDevicesPerUser = 3
 )
 
 // ChatMessageSender 聊天消息发送者信息
@@ -386,12 +386,9 @@ func (s *pushServiceImpl) pushViaJPushBatch(devices []*model.DeviceToken, params
 // 处理同设备多账号场景：registration_id（pushToken）是设备级标识，
 // 同一物理设备登录新账号时 pushToken 不变，需先失效其他用户对该 pushToken 的关联，
 // 避免给一个账号推送时同设备的其他账号也收到通知。
+// 每个用户最多保留 MaxDevicesPerUser 个活跃设备：注册后统一收敛到限额以内，
+// 既能处理达上限淘汰，也能收敛历史超额数据（如限额从 10 调整为 3 后的存量清理）。
 func (s *pushServiceImpl) RegisterDevice(ctx context.Context, userID string, deviceID string, deviceType model.DeviceType, pushToken string) error {
-	existing, err := s.deviceRepo.GetByUserID(userID)
-	if err == nil && len(existing) >= MaxDevicesPerUser {
-		return fmt.Errorf("exceeded maximum device limit (%d)", MaxDevicesPerUser)
-	}
-
 	// 失效其他用户/设备对同一 pushToken 的关联（防止跨账号误推）
 	if pushToken != "" {
 		if dErr := s.deviceRepo.DeactivateByPushToken(pushToken); dErr != nil {
@@ -413,7 +410,28 @@ func (s *pushServiceImpl) RegisterDevice(ctx context.Context, userID string, dev
 	}
 	deviceToken.UpdateLastUsed()
 
-	return s.deviceRepo.Upsert(deviceToken)
+	if err := s.deviceRepo.Upsert(deviceToken); err != nil {
+		return fmt.Errorf("failed to upsert device: %w", err)
+	}
+
+	// 收敛活跃设备数到 MaxDevicesPerUser 以内（保留最近使用的，淘汰超额的最旧设备）
+	// 覆盖两种场景：① 新设备注册导致超限；② 历史存量超额（限额调整后逐步收敛）
+	if evicted, err := s.deviceRepo.TrimActiveDevices(userID, MaxDevicesPerUser); err != nil {
+		zap.L().Warn("trim active devices failed",
+			zap.String("userID", userID),
+			zap.Int("limit", MaxDevicesPerUser),
+			zap.Error(err),
+		)
+	} else if evicted > 0 {
+		zap.L().Info("evicted oldest devices for device limit",
+			zap.String("userID", userID),
+			zap.String("deviceID", deviceID),
+			zap.Int64("evicted", evicted),
+			zap.Int("limit", MaxDevicesPerUser),
+		)
+	}
+
+	return nil
 }
 
 // UnregisterDevice 注销设备