feat: 新增多个服务类及工具类，重构部分代码结构

重构服务类结构，将分散的服务统一整合到service包下
新增ProjectConstant常量类及多个实体服务类
添加SecurityUtils安全工具类和BeanCacher工具类
优化部分UI控件和转换器的实现

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

@@ -0,0 +1,29 @@
+package com.ecep.contract.converter;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Lazy;
+import org.springframework.stereotype.Component;
+
+import com.ecep.contract.model.Company;
+import com.ecep.contract.service.CompanyService;
+
+import jakarta.annotation.PostConstruct;
+
+@Lazy
+@Component
+public class CompanyStringConverter extends EntityStringConverter<Company> {
+
+    @Lazy
+    @Autowired
+    CompanyService service;
+    public CompanyStringConverter() {
+
+    }
+
+    @PostConstruct
+    private void init() {
+        setInitialized(project -> service.findById(project.getId()));
+        setSuggestion(service::search);
+        setFromString(service::findByName);
+    }
+}