feat(declare): 同一申报项目进行中只允许一条申报

- 新增 DeclareGuardService：按已通过/未处理驳回/待审核数判重，申报项目行加锁防连点
- 9 张申报表补 declare_id / declare_status / declare_remark，提交时写入并随审核结果回写
- 新增撤回、作废（强制放行）接口；挑战杯团队成员按手机号判重
- 申报项目支持配置允许重复提交与最多同时条数
- 迁移脚本 sql/20261102_add_declare_uniqueness.sql（含存量回填与重复清单）

src/main/java/com/gxwebsoft/gxmu/model/DeclareCheckResult.java

@@ -0,0 +1,46 @@
+package com.gxwebsoft.gxmu.model;
+
+/**
+ * 申报提交前的校验结果。
+ *
+ * <p>三种形态：不适用（模块不在申报规则内）、被拒绝（带用户可读原因）、通过（带解析出的申报项目 id）。</p>
+ */
+public class DeclareCheckResult {
+    private final boolean applicable;
+    private final String error;
+    private final Integer declareId;
+
+    private DeclareCheckResult(boolean applicable, String error, Integer declareId) {
+        this.applicable = applicable;
+        this.error = error;
+        this.declareId = declareId;
+    }
+
+    public static DeclareCheckResult skip() {
+        return new DeclareCheckResult(false, null, null);
+    }
+
+    public static DeclareCheckResult reject(String error) {
+        return new DeclareCheckResult(true, error, null);
+    }
+
+    public static DeclareCheckResult pass(Integer declareId) {
+        return new DeclareCheckResult(true, null, declareId);
+    }
+
+    public boolean isApplicable() {
+        return applicable;
+    }
+
+    public boolean isRejected() {
+        return error != null;
+    }
+
+    public String getError() {
+        return error;
+    }
+
+    public Integer getDeclareId() {
+        return declareId;
+    }
+}