feat(crm): 添加客户编码自动生成功能

- 新增 selectMaxCustomerCode 方法查询最大客户编码
- 实现客户编码自动生成逻辑，支持纯数字和带前缀格式
- 添加正则表达式解析编码规则并递增末尾数字
- 集成编码生成功能到客户插入业务流程中

klp-crm/src/main/resources/mapper/CrmCustomerMapper.xml

@@ -23,5 +23,8 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
         <result property="delFlag" column="del_flag"/>
     </resultMap>
 
+    <select id="selectMaxCustomerCode" resultType="String">
+        SELECT customer_code FROM crm_customer WHERE del_flag = 0 ORDER BY LENGTH(customer_code) DESC, customer_code DESC LIMIT 1
+    </select>
 
 </mapper>