The sync delay slider spanned ±60s with 100ms steps, making fine
adjustment between e.g. 100ms and 200ms impractical on touch and mouse.
The slider now covers ±10s at 50ms per step (taps and D-pad included),
while the +/- step buttons still reach the ±60s absolute limit via
long-press, so existing large saved offsets keep working and display
their true value.
close#1907
edde746
2ff3b350ae