Tail/logs silently ignores future times in --since

[lionello]

defang tail --since=2222-11-11T11:11:11Z will just show regular tail since "now", and it was hard to see that I had made a typo in the time.

[nullfunc]

Give a proper error when the time stamp given doesn't make sense (i.e. in the future, not properly formatted, not an actual date)