Implement interactive calendar color picker

Backend enhancements:
- Add calendar_path field to CalendarEvent for color mapping
- Generate consistent colors for calendars using path-based hashing
- Update CalDAV parsing to associate events with their calendar paths
- Add 16-color palette with hash-based assignment algorithm

Frontend features:
- Interactive color picker with 4x4 grid of selectable colors
- Click color swatches to open dropdown with all available colors
- Instant color changes for both sidebar and calendar events
- Persistent color preferences using local storage
- Enhanced UX with hover effects and visual feedback

Styling improvements:
- Larger 16px color swatches for better clickability
- Professional color picker dropdown with smooth animations
- Dynamic event coloring based on calendar assignment
- Improved contrast with text shadows and borders
- Click-outside-to-close functionality for better UX

Users can now personalize their calendar organization with custom colors
that persist across sessions and immediately update throughout the app.

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

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

src/components/calendar.rs

@@ -1,7 +1,7 @@
 use yew::prelude::*;
 use chrono::{Datelike, Local, NaiveDate, Duration, Weekday};
 use std::collections::HashMap;
-use crate::services::calendar_service::CalendarEvent;
+use crate::services::calendar_service::{CalendarEvent, UserInfo};
 use crate::components::EventModal;
 
 #[derive(Properties, PartialEq)]
@@ -11,6 +11,8 @@ pub struct CalendarProps {
     pub on_event_click: Callback<CalendarEvent>,
     #[prop_or_default]
     pub refreshing_event_uid: Option<String>,
+    #[prop_or_default]
+    pub user_info: Option<UserInfo>,
 }
 
 #[function_component]
@@ -20,6 +22,21 @@ pub fn Calendar(props: &CalendarProps) -> Html {
     let selected_day = use_state(|| today);
     let selected_event = use_state(|| None::<CalendarEvent>);
     
+    // Helper function to get calendar color for an event
+    let get_event_color = |event: &CalendarEvent| -> String {
+        if let Some(user_info) = &props.user_info {
+            if let Some(calendar_path) = &event.calendar_path {
+                // Find the calendar that matches this event's path
+                if let Some(calendar) = user_info.calendars.iter()
+                    .find(|cal| &cal.path == calendar_path) {
+                    return calendar.color.clone();
+                }
+            }
+        }
+        // Default color if no match found
+        "#3B82F6".to_string()
+    };
+    
     let first_day_of_month = current_month.with_day(1).unwrap();
     let days_in_month = get_days_in_month(*current_month);
     let first_weekday = first_day_of_month.weekday();
@@ -118,10 +135,12 @@ pub fn Calendar(props: &CalendarProps) -> Html {
                                                         let title = event.get_title();
                                                         let is_refreshing = props.refreshing_event_uid.as_ref() == Some(&event.uid);
                                                         let class_name = if is_refreshing { "event-box refreshing" } else { "event-box" };
+                                                        let event_color = get_event_color(&event);
                                                         html! { 
                                                             <div class={class_name} 
                                                                  title={title.clone()} 
-                                                                 onclick={event_click}>
+                                                                 onclick={event_click}
+                                                                 style={format!("background-color: {}", event_color)}>
                                                                 {
                                                                     if is_refreshing {
                                                                         "🔄 Refreshing...".to_string()