Allow minimum time below 1 day (minutes/hours) for closed-conversation reply settings

Both the Email setting ("Create new conversations when customers reply to closed conversations," Settings > Channels > Email > Advanced) and the Messenger setting ("Prevent visitors replying to closed conversations," Settings > Channels > Messenger > General) only accept a minimum of 1 day. We need this configurable in minutes/hours (e.g. 30 min–1 hour) instead, so a reply shortly after closing doesn't reopen the original conversation. A 1-day window is too long for how quickly our conversations get closed and potentially replied to.