3468300: Allow "00:00" => "23:59" as min/max times in settings.
Up until now, the min_time/max_time in the settings form, are just text fields, that take data in AM/PM. This is problematic, because the code that parses it, fails when an editor has inserted "00:00". This commit changes the form to instead use time inputs, and ports any existing data to the new format. This also makes the new format 24h instead of 12h.
Closes #3468300