Fix NTP client stratum selection by setting stratumweight to 0.0

Co-authored-by: troglobit <183517+troglobit@users.noreply.github.com>

Author: Copilot

board/common/rootfs/etc/chrony/chrony.conf

@@ -25,3 +25,8 @@ rtcsync
 # Step the system clock instead of slewing it if the adjustment is
 # larger than one second, but only in the first three clock updates.
 makestep 1 3
+
+# Prioritize stratum over distance in source selection.
+# Default is 0.001, which means stratum only matters when distances differ
+# by >1ms. Setting to 0.0 ensures lower stratum sources are always preferred.
+stratumweight 0.0