Get the caller per-day action counts

Zero-filled and bucketed in the supplied IANA time zone. The window is clamped to the activity-log retention period, and windowDays reports what was actually served — label the UI from that rather than hardcoding a period.

curl -X GET "http://localhost:8000/api/timeline/activity-summary" \
  -H "Authorization: Bearer YOUR_TOKEN"

const response = await fetch("http://localhost:8000/api/timeline/activity-summary", {
  method: "GET",
  headers: {
    "Authorization": "Bearer YOUR_TOKEN"
  }
});