Returns appointments booked via calls or imported from connected calendars (Google, Outlook, Calendly, Square, Cal.com, GHL). Supports pagination (1-indexed page, max 100 per page — different from the 0-indexed offset used by /calls), plus filters by period ('upcoming' | 'past' | 'all'), agentId, calendarId, and free-text search across phone/email/title. Appointments only appear if at least one calendar is connected and enabled.