Set an end date for an invited user's aircraft visibility Merged

Problem:

When a user is granted aircraft visibility for a temporary need (a multi-day task force, a contractor's stint, a partner mutual-aid arrangement), there's no way to make the access expire automatically. Customers must remember to revoke later — and often don't.

Desired outcome:

The granter can specify an optional end date/time when granting aircraft access. After that point, visibility lapses automatically.

Proposed change:

Add an optional "visibility end" field to the share/grant dialog. Apply to both new invite acceptance and grants to existing users. Surface the expiry clearly in the recipient's view and the granter's audit trail. Send a reminder before expiry so it can be extended if needed.