Direct Booking Calendar: Improve Availability Display for Minimum-Stay Restrictions

The Direct Booking calendar currently grays out available dates if they do not meet a minimum-stay requirement based on the guest's initial selection. For example, with a 4-night minimum, selecting a start date can make subsequent available nights appear blocked or unavailable if the stay length isn't met yet.

This behavior is misleading as guests may assume the property is already booked and abandon the reservation. We need to update the calendar logic so that available dates remain visible and selectable. Instead of graying out dates, the system should only notify the guest of the minimum-stay requirement if they attempt to check out before the required number of nights, similar to the user experience on Airbnb.