feat: サイネージの生存判定のためdiagnosticを出力する

[yabuta]

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Description(required)

サイネージの生存判定のため1Hzでheartbeatのdiagを出力する

header:
  stamp:
    sec: 1703125968
    nanosec: 535917626
  frame_id: ''
status:
- level: "\0"
  name: 'signage: /system/signage_connection : signage heartbeat'
  message: signage is working
  hardware_id: none
  values: []

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[tkhmy]

LGTM