Add team members without recreating an add-on

What changed

What changed

Add eligible team members to an existing add-on. Adding its first staff member checks bookings that use that add-on and active checkout holds, rather than blocking on unrelated bookings.

What changed

Why this matters

• No need to recreate an unused add-on to attach a new team member.
• Existing booking assignments remain unchanged.
• Availability safeguards remain in place for resource changes and staff removals.