Fitbit health and fitness data integration. Fetch steps, heart rate, sleep, activity, calories, and trends from Fitbit Web API. Generate automated health reports and alerts. Requires FITBIT_CLIENT_ID, FITBIT_CLIENT_SECRET, FITBIT_ACCESS_TOKEN, FITBIT_REFRESH_TOKEN.

Fitbit健康与健身数据集成。通过Fitbit网页API获取步数、心率、睡眠、活动、卡路里及趋势数据，自动生成健康报告和提醒。需要提供FITBIT_CLIENT_ID、FITBIT_CLIENT_SECRET、FITBIT_ACCESS_TOKEN、FITBIT_REFRESH_TOKEN。