Problem:
The public aircraft sharing link only supports an expiry date that ends at the end of the selected day. Operators can't restrict access to a specific time window, and they can't schedule sharing to start later.
Desired outcome:
Operators want to control exactly when a public sharing link becomes active and when it expires, so visibility matches the operational window (e.g. a charter flight, a SAR mission, a ferry leg).
Proposed change:
Extend the sharing form to allow selecting an expiry date and time, and an optional start date and time. Sharing is inactive before the start time and stops working after the end time.
