Fetch questionnaires for a booking

Returns the questionnaires attached to a single booking or proposal, ordered by ID. An event_id is required — there is no franchise-wide listing.

Results are filtered automatically for the authenticated user. Admins see every questionnaire on the booking; staff see the ones with allow_staff_view; customers see the ones with allow_customer_view. Questionnaires restricted by show_before_or_after are also hidden outside their window, so a "before" questionnaire drops off the list once the booking starts.

Deleted questionnaires are never returned.

Required permission: assigned_event_read (when the authenticated user is assigned to the booking) or unassigned_event_read (otherwise).