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/util/BeanCacher.java

@@ -0,0 +1,22 @@
+package com.ecep.contract.util;
+
+import java.util.HashMap;
+
+import org.springframework.beans.BeansException;
+
+import com.ecep.contract.SpringApp;
+
+public class BeanCacher {
+
+    private HashMap<Class<?>, Object> cachedBeans = new HashMap<>();
+
+    @SuppressWarnings("unchecked")
+    public <T> T getBean(Class<T> requiredType) throws BeansException {
+        Object object = cachedBeans.get(requiredType);
+        if (object == null) {
+            object = SpringApp.getBean(requiredType);
+            cachedBeans.put(requiredType, object);
+        }
+        return (T) object;
+    }
+}