v0.13.0

Added

• Two more Insights Milestones: total strokes taken and peak heart rate. New stroke_count
  and heart_rate_max columns, captured on every sync going forward. Neither has a work/rest
  split to worry about — C2 doesn't report rest-period strokes or a separate rest heart rate, so
  both are plain per-session values (total strokes is a whole-session sum; peak HR is the highest
  single reading across history, with the date it happened).
• backfill_strokes_hr.py — same live-API backfill pattern as backfill_rest_meters.py, for the
  same reason (most historical workouts here were CSV-imported, no local raw_json to read this
  from). Unlike badges/journeys, Insights milestones are computed fresh on every page load rather
  than earned-once-and-locked, so there's nothing to retroactively correct here.