Implement comprehensive event series editing via modal

## Frontend Changes:
- Add EditAction enum (EditThis, EditFuture, EditAll) to event context menu
- Update context menu to show 3 edit options for recurring events
- Enhance EventCreationData with edit_scope and changed_fields tracking
- Update app component to handle EditAction types and pass to modal
- Add field change tracking infrastructure to CreateEventModal

## Backend Changes:
- Add changed_fields parameter to UpdateEventSeriesRequest for optimization
- Existing series endpoint already supports the three update types:
  - "this_only" - creates exception with EXDATE
  - "this_and_future" - creates new series with UNTIL on original
  - "all_in_series" - updates existing series in-place

## Implementation Details:
- Event context menu shows single edit option for non-recurring events
- Recurring events get three options: "Edit This Event", "Edit This and Future Events", "Edit All Events in Series"
- Modal tracks which fields user actually changed for efficient updates
- Backend series endpoint already has the logic for all three update scenarios
- Full RFC 5545 compliance with proper EXDATE and UNTIL handling

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

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

frontend/src/components/event_context_menu.rs

@@ -9,13 +9,20 @@ pub enum DeleteAction {
     DeleteSeries,
 }
 
+#[derive(Clone, PartialEq, Debug)]
+pub enum EditAction {
+    EditThis,
+    EditFuture,
+    EditAll,
+}
+
 #[derive(Properties, PartialEq)]
 pub struct EventContextMenuProps {
     pub is_open: bool,
     pub x: i32,
     pub y: i32,
     pub event: Option<VEvent>,
-    pub on_edit: Callback<()>,
+    pub on_edit: Callback<EditAction>,
     pub on_delete: Callback<DeleteAction>,
     pub on_close: Callback<()>,
 }
@@ -38,11 +45,11 @@ pub fn event_context_menu(props: &EventContextMenuProps) -> Html {
         .map(|event| event.rrule.is_some())
         .unwrap_or(false);
 
-    let on_edit_click = {
+    let create_edit_callback = |action: EditAction| {
         let on_edit = props.on_edit.clone();
         let on_close = props.on_close.clone();
         Callback::from(move |_: MouseEvent| {
-            on_edit.emit(());
+            on_edit.emit(action.clone());
             on_close.emit(());
         })
     };
@@ -62,9 +69,29 @@ pub fn event_context_menu(props: &EventContextMenuProps) -> Html {
             class="context-menu" 
             style={style}
         >
-            <div class="context-menu-item" onclick={on_edit_click}>
-                {"Edit Event"}
-            </div>
+            {
+                if is_recurring {
+                    html! {
+                        <>
+                            <div class="context-menu-item" onclick={create_edit_callback(EditAction::EditThis)}>
+                                {"Edit This Event"}
+                            </div>
+                            <div class="context-menu-item" onclick={create_edit_callback(EditAction::EditFuture)}>
+                                {"Edit This and Future Events"}
+                            </div>
+                            <div class="context-menu-item" onclick={create_edit_callback(EditAction::EditAll)}>
+                                {"Edit All Events in Series"}
+                            </div>
+                        </>
+                    }
+                } else {
+                    html! {
+                        <div class="context-menu-item" onclick={create_edit_callback(EditAction::EditThis)}>
+                            {"Edit Event"}
+                        </div>
+                    }
+                }
+            }
             {
                 if is_recurring {
                     html! {