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

server/src/main/java/com/ecep/contract/util/SecurityUtils.java

@@ -0,0 +1,15 @@
+package com.ecep.contract.util;
+
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.security.core.userdetails.User;
+
+public class SecurityUtils {
+    public static User getCurrentUser() {
+        return (User) SecurityContextHolder.getContext().getAuthentication().getPrincipal();
+    }
+
+    public static boolean currentUserHasRole(String role) {
+        return getCurrentUser().getAuthorities().stream()
+                .anyMatch(grantedAuthority -> grantedAuthority.getAuthority().equals(role));
+    }
+}