Refactor event modal into standalone component

- Created dedicated EventModal component in src/components/event_modal.rs
- Extracted modal logic and styling from calendar component for better separation
- Updated data flow to pass full CalendarEvent objects instead of strings
- Added PartialEq derive to CalendarEvent for component props
- Updated service layer to group events by CalendarEvent objects
- Enhanced event click handling to show detailed event information
- Modal displays title, description, location, start/end times, and status
- Maintained existing modal styling and user interaction patterns

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

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

src/components/mod.rs

@@ -1,7 +1,9 @@
 pub mod login;
 pub mod register;
 pub mod calendar;
+pub mod event_modal;
 
 pub use login::Login;
 pub use register::Register;
-pub use calendar::Calendar;
+pub use calendar::Calendar;
+pub use event_modal::EventModal;