fix(stats): reject sub-threshold gps drift

go/vehicle-gateway/cmd/stats-backfill/main.go

@@ -622,7 +622,7 @@ ORDER BY ts ASC`, ident(cfg.TDengineDatabase), strings.Join(where, " AND "))
 	}
 	added := 0
 	for target, state := range states {
-		if state.usableSegments == 0 {
+		if !stats.GPSMileageCandidateEligible(state.distanceKM, state.usableSegments) {
 			continue
 		}
 		parts := strings.SplitN(target, "|", 2)