curl -X PUT "https://app.talkover.ai/api/v1/calendars/calendar-uuid-1/availability-rules/rule-uuid-1" \
  -H "Authorization: Bearer talq_your_environment_token_here" \
  -H "Content-Type: application/json" \
  -d '{ "end_time": "18:00" }'

{
  "success": true,
  "data": {
    "id": "rule-uuid-1",
    "end_time": "18:00"
  }
}