fix: export cdr msd issue

src/modules/network_data/service/cdr_event_mf.go

@@ -145,8 +145,17 @@ func (r CDREventMF) ExportXlsx(rows []model.CDREventMF, fileName, language strin
 		}
 		// MSD-最小数据集
 		msd := ""
-		if v, ok := cdrJSON["msd"]; ok && v != nil {
+		if v, ok := cdrJSON["msdData"]; ok && v != nil && v != "" {
-			msd = v.(string)
+			switch vv := v.(type) {
+			case string:
+				msd = vv
+			case json.RawMessage:
+				msd = string(vv)
+			case map[string]interface{}:
+				// 如果是对象，序列化为json.RawMessage
+				b, _ := json.Marshal(vv)
+				msd = string(b)
+			}
 		}
 		dataCells = append(dataCells, map[string]any{
 			"A" + idx: row.ID,