Fetch checklist items

Returns a paginated list of checklist items visible to the authenticated user. Results can be scoped to a single checklist, filtered by status, assignment, or full-text search, and sorted by due date, event date, or recency.

Visibility is determined automatically based on the authenticated user's role: admins see every item; staff see items on their personal checklist, items assigned to them, and items on event or franchise checklists they have view access to; customers see items on their event checklists where customer view is allowed.

The response includes meta.total_count and meta.per_page for pagination.