Validate return and exchange policies and check order eligibility
验证订单是否符合退换货条件：
{
"order_id": "20240228123456",
"service_type": "return",
"reason": "quality_issue"
}
{
"structured": {
"eligible": true,
"validation_results": {...},
"fee_policy": {...}
},
"text": "该订单符合退货条件..."
}