Refactor calendar component into modular architecture with view switching

- Split monolithic Calendar component into focused sub-components:
  - CalendarHeader: Navigation buttons and title display
  - MonthView: Monthly calendar grid layout and event rendering
  - WeekView: Weekly calendar view with full-height day containers
- Add ViewMode enum for Month/Week view switching in sidebar dropdown
- Fix event styling by correcting CSS class from "event" to "event-box"
- Implement proper week view layout with full-height day containers
- Maintain all existing functionality: event handling, context menus, localStorage persistence

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/mod.rs

@@ -1,5 +1,8 @@
 pub mod login;
 pub mod calendar;
+pub mod calendar_header;
+pub mod month_view;
+pub mod week_view;
 pub mod event_modal;
 pub mod create_calendar_modal;
 pub mod context_menu;
@@ -12,12 +15,15 @@ pub mod route_handler;
 
 pub use login::Login;
 pub use calendar::Calendar;
+pub use calendar_header::CalendarHeader;
+pub use month_view::MonthView;
+pub use week_view::WeekView;
 pub use event_modal::EventModal;
 pub use create_calendar_modal::CreateCalendarModal;
 pub use context_menu::ContextMenu;
 pub use event_context_menu::{EventContextMenu, DeleteAction};
 pub use calendar_context_menu::CalendarContextMenu;
 pub use create_event_modal::{CreateEventModal, EventCreationData, EventStatus, EventClass, ReminderType, RecurrenceType};
-pub use sidebar::Sidebar;
+pub use sidebar::{Sidebar, ViewMode};
 pub use calendar_list_item::CalendarListItem;
 pub use route_handler::RouteHandler;