fix: show overnight appointments on each covered calendar day

src/modules/appointment-calendar/calendar.ts

@@ -1,5 +1,13 @@
 export type CalendarMode = 'month' | 'week'
 
+/** End times are exclusive; a slot ending at midnight does not occupy the next day. */
+export function occursOnDate(startDate: string, endAt: string | undefined, date: string): boolean {
+  if (date === startDate) return true
+  if (date < startDate || !endAt) return false
+  const endDate = endAt.slice(0, 10)
+  return date < endDate || (date === endDate && /[1-9]/.test(endAt.slice(11)))
+}
+
 /** Calendar dates are warehouse-local dates, never UTC conversions. */
 export function dateKey(date: Date): string {
   return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}-${String(date.getDate()).padStart(2, '0')}`