feat: 添加合约文件类型服务及错误处理改进

refactor: 重构合约文件类型相关代码，优化错误处理逻辑

fix: 修复WebSocket会话未绑定用户时的错误处理

style: 调整代码格式，提高可读性

docs: 更新部分代码注释

test: 添加合约文件类型服务的测试用例

chore: 移除无用代码，清理项目结构

client/src/main/java/com/ecep/contract/vm/ContractFileTypeLocalViewModel.java

@@ -0,0 +1,51 @@
+package com.ecep.contract.vm;
+
+import java.util.Objects;
+
+import com.ecep.contract.ContractFileType;
+import com.ecep.contract.model.ContractFileTypeLocal;
+
+import javafx.beans.property.SimpleObjectProperty;
+import javafx.beans.property.SimpleStringProperty;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+
+@Data
+@EqualsAndHashCode(callSuper = false)
+public class ContractFileTypeLocalViewModel extends IdentityViewModel<ContractFileTypeLocal> {
+    private SimpleObjectProperty<ContractFileType> type = new SimpleObjectProperty<>();
+    private SimpleStringProperty suggestFileName = new SimpleStringProperty();
+    private SimpleStringProperty lang = new SimpleStringProperty();
+    private SimpleStringProperty value = new SimpleStringProperty();
+
+    @Override
+    protected void updateFrom(ContractFileTypeLocal v) {
+        super.updateFrom(v);
+        type.set(v.getType());
+        suggestFileName.set(v.getSuggestFileName());
+        lang.set(v.getLang());
+        value.set(v.getValue());
+    }
+
+    @Override
+    public boolean copyTo(ContractFileTypeLocal v) {
+        boolean ret = super.copyTo(v);
+        if (!Objects.equals(type.get(), v.getType())) {
+            v.setType(type.get());
+            ret = true;
+        }
+        if (!Objects.equals(suggestFileName.get(), v.getSuggestFileName())) {
+            v.setSuggestFileName(suggestFileName.get());
+            ret = true;
+        }
+        if (!Objects.equals(lang.get(), v.getLang())) {
+            v.setLang(lang.get());
+            ret = true;
+        }
+        if (!Objects.equals(value.get(), v.getValue())) {
+            v.setValue(value.get());
+            ret = true;
+        }
+        return ret;
+    }
+}