fix: 修复SegmentConfig Jackson多态序列化type冲突

- 移除SegmentConfig中与@JsonTypeInfo冲突的type字段
- buildSegment改用instanceof替代getType()
- 避免序列化时type覆盖为null导致反序列化失败

nl-module-base/nl-module-base-server/src/main/java/cn/code/nl/module/base/service/codegen/CodeGenServiceImpl.java

@@ -61,12 +61,14 @@ public class CodeGenServiceImpl implements CodeGenService {
      * 根据段类型分发处理，生成段值
      */
     private String buildSegment(CodeRuleDO rule, SegmentConfig segment) {
-        return switch (segment.getType()) {
-            case "PREFIX" -> buildPrefixSegment((PrefixSegment) segment);
-            case "DATE" -> buildDateSegment((DateSegment) segment);
-            case "SEQUENCE" -> buildSequenceSegment(rule, (SequenceSegment) segment);
-            default -> throw new IllegalArgumentException("不支持的段类型: " + segment.getType());
-        };
+        if (segment instanceof PrefixSegment) {
+            return buildPrefixSegment((PrefixSegment) segment);
+        } else if (segment instanceof DateSegment) {
+            return buildDateSegment((DateSegment) segment);
+        } else if (segment instanceof SequenceSegment) {
+            return buildSequenceSegment(rule, (SequenceSegment) segment);
+        }
+        throw new IllegalArgumentException("不支持的段类型: " + segment.getClass().getSimpleName());
     }
 
     /**

nl-module-base/nl-module-base-server/src/main/java/cn/code/nl/module/base/service/codegen/dto/SegmentConfig.java

@@ -5,22 +5,18 @@ import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import lombok.Data;
 
 /**
- * 分段配置基类，使用 Jackson 多态序列化/反序列化
+ * 分段配置基类，使用 Jackson 多态序列化/反序列化。
+ * 注意：type 字段由 @JsonTypeInfo 自动管理，不要在子类中重复定义，
+ * 否则会导致序列化时 type 被覆盖为 null，反序列化时找不到子类型。
  *
  * @author zhouz
  */
 @Data
-@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type", visible = true)
 @JsonSubTypes({
     @JsonSubTypes.Type(value = PrefixSegment.class, name = "PREFIX"),
     @JsonSubTypes.Type(value = DateSegment.class, name = "DATE"),
     @JsonSubTypes.Type(value = SequenceSegment.class, name = "SEQUENCE")
 })
 public abstract class SegmentConfig {
-
-    /**
-     * 段类型：PREFIX / DATE / SEQUENCE
-     */
-    private String type;
-
 }