fix: resolve infinite loop and week calculation issues in EventModal

- Fix infinite loop in EventModal useEffect by using useRef for userPersonnalCalendars
- Fix weekStart calculation in putEventAsync to use Monday as first day (consistent with FullCalendar firstDay=1)
- Add computeWeekRange utility function for consistent week calculations
- Improve state reset logic when closing EventModal popup
- Ensure repeat checkbox state is properly reset to prevent stale repetition data

src/utils/dateUtils.ts

@@ -52,3 +52,10 @@ export const computeStartOfTheWeek = (date: Date): Date => {
   startOfWeek.setHours(0, 0, 0, 0);
   return startOfWeek;
 };
+
+export const computeWeekRange = (date: Date): { start: Date; end: Date } => {
+  const weekStart = computeStartOfTheWeek(date);
+  const weekEnd = new Date(weekStart);
+  weekEnd.setDate(weekStart.getDate() + 7);
+  return { start: weekStart, end: weekEnd };
+};