fix(calendar): initialize selected date in ScheduleCalendar component if not set

- Added useEffect to set the selected date to the current date if it is not already defined.
- Imported useEffect alongside useState for managing component lifecycle.

apps/web/components/schedule/calendar.tsx

@@ -6,7 +6,7 @@ import { useDateTimeStore } from '@/stores/datetime';
 import { Calendar } from '@repo/ui/components/ui/calendar';
 import { getDateUTCRange } from '@repo/utils/datetime-format';
 import dayjs from 'dayjs';
-import { useState } from 'react';
+import { useEffect, useState } from 'react';
 
 export function ScheduleCalendar() {
   const { data: { customer } = {} } = useCustomerQuery();
@@ -14,6 +14,12 @@ export function ScheduleCalendar() {
   const selectedDate = useDateTimeStore((store) => store.date);
   const setSelectedDate = useDateTimeStore((store) => store.setDate);
 
+  useEffect(() => {
+    if (!selectedDate) {
+      setSelectedDate(new Date());
+    }
+  }, [selectedDate, setSelectedDate]);
+
   const [currentMonthDate, setCurrentMonthDate] = useState(new Date());
 
   const { endOfMonth, startOfMonth } = getDateUTCRange(currentMonthDate).month();