fix: use the local date for the event modal's default start and end (#27779)

src/lib/components/calendar/CalendarEventModal.svelte

@@ -100,10 +100,10 @@
 				endTime = nsToTimeStr(endNs);
 			} else {
 				const now = new Date();
-				startDate = now.toISOString().slice(0, 10);
+				startDate = nsToDateStr(now.getTime() * NS);
 				startTime = now.toTimeString().slice(0, 5);
 				const later = new Date(now.getTime() + 60 * 60 * 1000);
-				endDate = later.toISOString().slice(0, 10);
+				endDate = nsToDateStr(later.getTime() * NS);
 				endTime = later.toTimeString().slice(0, 5);
 			}
 			allDay = false;