Implement comprehensive calendar UX improvements

- Add time range display to week view events showing "start - end" format
- Optimize time display with smart AM/PM formatting to reduce redundancy
- Fix context menu overlap by adding stop_propagation to event handlers
- Implement persistent view mode (Month/Week) across page refreshes using localStorage
- Replace month-based tracking with intelligent selected date tracking
- Add day selection in month view with visual feedback and click handlers
- Fix view switching to navigate to week containing selected day, not first week of month
- Separate selected_date from display_date for proper context switching
- Simplify week view header to show "Month Year" instead of "Week of Month Day"
- Add backward compatibility for existing localStorage keys

Greatly improves calendar navigation and user experience with persistent state

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

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

src/components/calendar_header.rs

@@ -14,14 +14,7 @@ pub struct CalendarHeaderProps {
 
 #[function_component(CalendarHeader)]
 pub fn calendar_header(props: &CalendarHeaderProps) -> Html {
-    let title = match props.view_mode {
-        ViewMode::Month => {
-            format!("{} {}", get_month_name(props.current_date.month()), props.current_date.year())
-        },
-        ViewMode::Week => {
-            format!("Week of {} {}", get_month_name(props.current_date.month()), props.current_date.day())
-        },
-    };
+    let title = format!("{} {}", get_month_name(props.current_date.month()), props.current_date.year());
 
     html! {
         <div class="calendar-header">