Refactor app.rs by extracting components for better organization

Split monolithic app.rs into focused, reusable components:
- Sidebar component for user info, navigation and calendar management
- CalendarListItem component for individual calendar items with color picker
- RouteHandler component to eliminate duplicated routing logic
- Reduced app.rs from 645 to 338 lines (47% reduction)
- Improved separation of concerns and maintainability
- Clean props-based component communication

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

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

src/components/mod.rs

@@ -3,9 +3,15 @@ pub mod calendar;
 pub mod event_modal;
 pub mod create_calendar_modal;
 pub mod context_menu;
+pub mod sidebar;
+pub mod calendar_list_item;
+pub mod route_handler;
 
 pub use login::Login;
 pub use calendar::Calendar;
 pub use event_modal::EventModal;
 pub use create_calendar_modal::CreateCalendarModal;
-pub use context_menu::ContextMenu;
+pub use context_menu::ContextMenu;
+pub use sidebar::Sidebar;
+pub use calendar_list_item::CalendarListItem;
+pub use route_handler::RouteHandler;