Add comprehensive iCal properties support to event creation modal

Enhanced the create event modal to include all major iCalendar properties:
- Event status (confirmed/tentative/cancelled)
- Privacy classification (public/private/confidential)
- Priority levels (0-9 numeric scale)
- Organizer email field
- Attendees list (comma-separated emails)
- Categories (comma-separated tags)
- Reminder options (none to 1 week before)
- Recurrence patterns (none/daily/weekly/monthly/yearly)

Updated backend to parse and handle all new fields, with proper enum conversion
and comma-separated list parsing. Events now generate complete iCal data with
STATUS, CLASS, PRIORITY, ORGANIZER, ATTENDEE, CATEGORIES, VALARM, and RRULE properties.

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

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

src/services/calendar_service.rs

@@ -599,6 +599,14 @@ impl CalendarService {
         end_time: String,
         location: String,
         all_day: bool,
+        status: String,
+        class: String,
+        priority: Option<u8>,
+        organizer: String,
+        attendees: String,
+        categories: String,
+        reminder: String,
+        recurrence: String,
         calendar_path: Option<String>
     ) -> Result<(), String> {
         let window = web_sys::window().ok_or("No global window exists")?;
@@ -616,6 +624,14 @@ impl CalendarService {
             "end_time": end_time,
             "location": location,
             "all_day": all_day,
+            "status": status,
+            "class": class,
+            "priority": priority,
+            "organizer": organizer,
+            "attendees": attendees,
+            "categories": categories,
+            "reminder": reminder,
+            "recurrence": recurrence,
             "calendar_path": calendar_path
         });