feat: 添加合同文件类型相关类和文档

添加了VendorCatalogStringConverter转换器类、ContractFileTypeListCell列表单元格类和ContractFileTypeTableCell表格单元格类，并创建了相关文档文件

client/src/main/java/com/ecep/contract/controller/list/cell/ContractFileTypeListCell.java

@@ -0,0 +1,4 @@
+package com.ecep.contract.controller.list.cell;
+
+public class ContractFileTypeListCell {
+}

client/src/main/java/com/ecep/contract/controller/table/cell/ContractFileTypeTableCell.java

@@ -0,0 +1,4 @@
+package com.ecep.contract.controller.table.cell;
+
+public class ContractFileTypeTableCell {
+}

client/src/main/java/com/ecep/contract/converter/VendorCatalogStringConverter.java

@@ -0,0 +1,4 @@
+package com.ecep.contract.converter;
+
+public class VendorCatalogStringConverter {
+}