curl --request GET \
  --url http://0.0.0.0:3000/v1/billing/usage \
  --header 'Authorization: Bearer <token>'

{
  "plan": {
    "name": "Pro"
  },
  "usage": {
    "config_entries": {
      "current": 2,
      "limit": 10
    },
    "devices": {
      "current": 5,
      "limit": null
    },
    "automations": {
      "current": 3,
      "limit": 20
    }
  }
}