Support date/time ranges in automation rules

Problem
Automation rules can only be triggered within daily time windows, not for specific date/time ranges. This prevents automating PTO rules or temporarily activating team availability settings.

Request
Add support for date/time range conditions in rules (e.g., "activate from 6/26 at 5:30 PM to 7/03 at 6 PM"). Rule actions could include moving emails to shared inboxes, sending out-of-office messages, or archiving in personal inboxes.

Context
This would align with Front's "Time Off" function and reduce manual rule management.