Support Business Hours That Extend Overnight (e.g., 18:00 → 00:00 or later)

Users who operate in the evening or overnight (e.g., starting at 18:00 and ending at 00:00 or later) currently cannot configure business hours intuitively.

The time picker prevents selecting late-night start times (such as 18:00) unless an end time is already set, and it does not allow selecting 00:00 (midnight) as a clear endpoint.

This makes it difficult for teams with night-shift or after-hours schedules to accurately define their availability.

Requested improvements:

• Allow selecting 00:00 as a standard end time.

• Allow setting the start time later than 4:30 without requiring a pre-selected end time.

• Full support for overnight time ranges (e.g., 18:00–02:00).