Implement drag-to-move functionality for events in week view with CalDAV server integration

- Add drag-to-move event handlers to existing events in week view
- Extend drag state management to support both create and move operations
- Implement visual feedback with event preview during drag and hidden original
- Calculate new start/end times while preserving event duration
- Add CalDAV server update integration via calendar service
- Wire event update callbacks through component hierarchy (WeekView → Calendar → RouteHandler → App)
- Preserve all original event properties (title, description, location, reminders, etc.)
- Handle timezone conversion from local to UTC for server storage
- Add error handling with user feedback and success confirmation
- Include moving event CSS styling with enhanced visual feedback

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

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

src/components/calendar.rs

@@ -24,6 +24,8 @@ pub struct CalendarProps {
     #[prop_or_default]
     pub on_create_event_request: Option<Callback<EventCreationData>>,
     #[prop_or_default]
+    pub on_event_update_request: Option<Callback<(CalendarEvent, chrono::NaiveDateTime, chrono::NaiveDateTime)>>,
+    #[prop_or_default]
     pub context_menus_open: bool,
 }
 
@@ -188,6 +190,16 @@ pub fn Calendar(props: &CalendarProps) -> Html {
             show_create_modal.set(true);
         })
     };
+    
+    // Handle drag-to-move event
+    let on_event_update = {
+        let on_event_update_request = props.on_event_update_request.clone();
+        Callback::from(move |(event, new_start, new_end): (CalendarEvent, chrono::NaiveDateTime, chrono::NaiveDateTime)| {
+            if let Some(callback) = &on_event_update_request {
+                callback.emit((event, new_start, new_end));
+            }
+        })
+    };
 
     html! {
         <div class={classes!("calendar", match props.view { ViewMode::Week => Some("week-view"), _ => None })}>
@@ -238,6 +250,7 @@ pub fn Calendar(props: &CalendarProps) -> Html {
                             on_event_context_menu={props.on_event_context_menu.clone()}
                             on_calendar_context_menu={props.on_calendar_context_menu.clone()}
                             on_create_event={Some(on_create_event)}
+                            on_event_update={Some(on_event_update)}
                             context_menus_open={props.context_menus_open}
                             time_increment={*time_increment}
                         />