Layout: map + charts stacked left, stats panel (2-col) on the right.
Cadence moved to last stat. Charts sit directly below the map.
Speed coloring: most FIT files don't record per-second speed, leaving
timeseries speed_kmh all-null and the hover link dead. Fix: derive speed
from consecutive GPS coordinates (haversine + 5-pt moving average) when
the device didn't record it. Add --backfill-speed render flag to retrofit
existing timeseries files.
Davide Scaini
14a4a0b994