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/app.rs

@@ -2,7 +2,7 @@ use yew::prelude::*;
 use yew_router::prelude::*;
 use gloo_storage::{LocalStorage, Storage};
 use crate::components::{Login, Register, Calendar};
-use crate::services::CalendarService;
+use crate::services::{CalendarService, CalendarEvent};
 use std::collections::HashMap;
 use chrono::{Local, NaiveDate, Datelike};
 
@@ -107,7 +107,7 @@ pub fn App() -> Html {
 
 #[function_component]
 fn CalendarView() -> Html {
-    let events = use_state(|| HashMap::<NaiveDate, Vec<String>>::new());
+    let events = use_state(|| HashMap::<NaiveDate, Vec<CalendarEvent>>::new());
     let loading = use_state(|| true);
     let error = use_state(|| None::<String>);