Feat/ implement comprehensive calendar

Architecture & Navigation

• Add comprehensive calendar types and Zustand store for centralized appointment management • Implement smart navigation with proper routing structure under (tabs)/calendar/ • Create modular calendar system with 3 focused screens (CalendarScreen, AgendaViewScreen, AppointmentDetailsScreen) • Update navigation routing across all calendar screens for smooth user flow • Maintain clean folder structure with separated constants, utils, and component organization • Implement code using TypeScript throughout for type safety and better development experience

Calendar Management Features

• Add complete appointment system with filtering by type, status, and date range • Show monthly and list view modes with smooth animated transitions • Update appointment details with confirm presence and reschedule functionality • Add advanced search capabilities across appointment titles, locations, and contacts • Create day agenda view with week navigation and appointment cards • Implement real-time status updates with optimistic UI changes

Components Architecture

• Main Screens: CalendarScreen, AgendaViewScreen, AppointmentDetailsScreen • Core Components: AppointmentCard, AnimatedAppointmentCard, AppointmentDetailsCard, AppointmentActionsSection • Specialized Components: CalendarContent, CalendarFilterBar, CalendarHeader, CalendarDay, CalendarMonthView, CalendarEmptyState, DayAppointmentsModal, RescheduleModal

Closes VSN-1271