fix distance calculation

bincio/extract/metrics.py

@@ -130,7 +130,11 @@ def _gps_stats(
     if not has_data:
         return device_dist, None, None, None
 
-    distance_m = device_dist if device_dist is not None else round(total_dist_m, 1)
+    # Fall back to haversine distance if device recorded 0 but we computed real GPS distance
+    if device_dist is not None and device_dist > 0:
+        distance_m = device_dist
+    else:
+        distance_m = round(total_dist_m, 1) if total_dist_m > 0 else device_dist
     moving_time_s = moving_s if moving_s > 0 else None
     avg_speed_kmh = (moving_dist_m / moving_s) * 3.6 if moving_s > 0 else None
     # Prefer device speed for max (more stable than GPS-derived per-second spikes)