fix(channel-monitor-v2): default hide_throughput true for privacy parity

Align InitializeDefaultSettings and parseSettings with the public-settings
path and migration 206 so admin and user views agree when the key is unset.

backend/internal/service/setting_parse.go

@@ -187,7 +187,7 @@ func (s *SettingService) InitializeDefaultSettings(ctx context.Context) error {
 		SettingKeyChannelMonitorEnabled:                "true",
 		SettingKeyChannelMonitorMode:                   ChannelMonitorModeV2,
 		SettingKeyChannelMonitorDefaultIntervalSeconds: "60",
-		SettingKeyChannelMonitorHideThroughput:         "false",
+		SettingKeyChannelMonitorHideThroughput:         "true",
 
 		// Available channels feature (default disabled; opt-in)
 		SettingKeyAvailableChannelsEnabled: "false",
@@ -787,7 +787,9 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 	result.ChannelMonitorDefaultIntervalSeconds = parseChannelMonitorInterval(
 		settings[SettingKeyChannelMonitorDefaultIntervalSeconds],
 	)
-	result.ChannelMonitorHideThroughput = settings[SettingKeyChannelMonitorHideThroughput] == "true"
+	// 默认隐藏吞吐（迁移 206 的隐私默认）：未配置时必须与 setting_public.go 的
+	// 公开读取路径给出同一个值，否则管理端看到“未隐藏”而用户端实际已隐藏。
+	result.ChannelMonitorHideThroughput = !isFalseSettingValue(settings[SettingKeyChannelMonitorHideThroughput])
 
 	// Available channels feature (default: disabled; strict true)
 	result.AvailableChannelsEnabled = settings[SettingKeyAvailableChannelsEnabled] == "true"