feat(flow): 回调链路迁平台 flow-callback starter + 表单级流程绑定

- 回调迁 starter（2026-09-20）：删本地实现 FlowCallbackService/Controller/
  FilterConfiguration 及旧测试，X-Flw 验签/幂等/乱序门由 starter 承担，
  业务映射入 SvcFlowCallbackHandler（biz-type svc_item）；端点仍 /callback/flow，
  存量注册 callback_url 不变、secret 零轮换，镜像表 flow_callback_reg
  由 sql/20260920_flow_callback_starter_migration.sql 迁移
- 表单级流程绑定：ServiceForm 增 flowGuid，事项未绑流程时回退取绑定表单
  最新版本（effectiveFlowGuid），绑定校验/在线办理口径同步
- FlowReconcileJob/FlowCenterClient/OpenApiAuthEnforceConfiguration 等
  SDK 适配微调；补 .gitignore（target/、日志）
- 全量 mvn test 本地绿（含新增 SvcFlowCallbackHandlerTest/
  ServiceItemEffectiveFlowTest）

src/main/java/com/yunhai/svchall/job/FlowReconcileJob.java

@@ -4,7 +4,7 @@ import com.yunhai.svchall.entity.ServiceApply;
 import com.yunhai.svchall.enums.ApplyFlowStatusEnum;
 import com.yunhai.svchall.repository.ServiceApplyRepository;
 import com.yunhai.svchall.service.FlowClient;
-import com.yunhai.svchall.service.impl.FlowCallbackService;
+import com.yunhai.svchall.service.impl.SvcFlowCallbackHandler;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.scheduling.annotation.Scheduled;
@@ -56,7 +56,7 @@ public class FlowReconcileJob {
             }
             try {
                 Map<String, Object> remote = flowClient.getInstanceByBiz(
-                        apply.getSchId(), FlowCallbackService.BIZ_TYPE, String.valueOf(apply.getId()));
+                        apply.getSchId(), SvcFlowCallbackHandler.BIZ_TYPE, String.valueOf(apply.getId()));
                 if (remote == null) {
                     continue;
                 }