Complete event modal migration: remove original and rename V2

Remove the original create_event_modal.rs and rename create_event_modal_v2.rs
to complete the modal migration started earlier. This eliminates duplicate code
and consolidates to a single, clean event modal implementation.

Changes:
- Remove original create_event_modal.rs (2,300+ lines)
- Rename create_event_modal_v2.rs → create_event_modal.rs
- Update component/function names: CreateEventModalV2 → CreateEventModal
- Fix all imports in app.rs and calendar.rs
- Add missing to_create_event_params() method to EventCreationData
- Resolve EditAction type conflicts between modules
- Clean up duplicate types and unused imports
- Maintain backwards compatibility with EventCreationData export

Result: -2440 lines, +160 lines - massive code cleanup with zero functionality loss.

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

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

frontend/src/app.rs

@@ -1,7 +1,6 @@
 use crate::components::{
-    CalendarContextMenu, ContextMenu, CreateCalendarModal, CreateEventModalV2, DeleteAction,
-    EditAction, EventClass, EventContextMenu, EventCreationData, EventStatus, RecurrenceType,
-    ReminderType, RouteHandler, Sidebar, Theme, ViewMode,
+    CalendarContextMenu, ContextMenu, CreateCalendarModal, CreateEventModal, DeleteAction,
+    EditAction, EventContextMenu, EventCreationData, RouteHandler, Sidebar, Theme, ViewMode,
 };
 use crate::components::sidebar::{Style};
 use crate::models::ical::VEvent;
@@ -1031,7 +1030,7 @@ pub fn App() -> Html {
                     on_create_event={on_create_event_click}
                 />
 
-                <CreateEventModalV2
+                <CreateEventModal
                     is_open={*create_event_modal_open}
                     selected_date={(*selected_date_for_event).clone()}
                     initial_start_time={None}