refactore(NotificationsOverview): add reset hours for email limit

Show remaining hours until the account's email limit resets for the user

See: BEDS-870

frontend/components/notifications/NotificationsOverview.vue

@@ -27,8 +27,7 @@ const notificationsTotal = computed(() => {
 const { user } = useUserStore()
 const mailLimit = computed(() => user.value?.premium_perks.email_notifications_per_day ?? 0)
 
-// TODO: replace with actual hours value when we get the endpoint.
-const resetHours = ref(12)
+const resetHours = computed(() => overview.value?.next_email_count_reset_timestamp ?? 0)
 const tooltipEmail = computed(() => {
   return $t('notifications.overview.email_tooltip', {
     hours: resetHours.value,