Fix series RRULE updates: editing 'all events' now properly updates original series RRULE

- Backend now updates RRULE when recurrence_count or recurrence_end_date parameters are provided
- Fixed update_entire_series() to modify COUNT/UNTIL instead of preserving original RRULE
- Added comprehensive RRULE parsing functions to extract existing frequency, interval, count, until, and BYDAY components
- Fixed frontend parameter mapping to pass recurrence parameters through update_series calls
- Resolves issue where changing recurring event from 5 to 7 occurrences kept original COUNT=5

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

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

frontend/src/app.rs

@@ -478,7 +478,10 @@ pub fn App() -> Html {
                                     params.13, // categories
                                     params.14, // reminder
                                     params.15, // recurrence
-                                    params.17, // calendar_path (skipping recurrence_days)
+                                    params.16, // recurrence_days
+                                    params.18, // recurrence_count
+                                    params.19, // recurrence_until
+                                    params.17, // calendar_path
                                     scope,
                                     event_data_for_update.occurrence_date.map(|d| d.format("%Y-%m-%d").to_string()), // occurrence_date
                                 )
@@ -759,6 +762,9 @@ pub fn App() -> Html {
                                             original_event.categories.join(","),
                                             reminder_str.clone(),
                                             recurrence_str.clone(),
+                                            vec![false; 7],
+                                            None,
+                                            None,
                                             original_event.calendar_path.clone(),
                                             scope.clone(),
                                             occurrence_date,