feat(app): application_info app_code 写入口守卫（已登记拒改名/拒清空，初次登记唯一性保持）

src/main/java/com/yunhai/userbase/repository/ApplicationInfoRepository.java

@@ -17,6 +17,12 @@ import java.util.List;
  * @description
  */
 public interface ApplicationInfoRepository  extends JpaRepository<ApplicationInfo, Integer>, JpaSpecificationExecutor<ApplicationInfo> {
+    /** 读取持久化标识快照；禁止查询前自动 flush 掉待校验的实体改名。 */
+    @Query("SELECT a.appCode FROM ApplicationInfo a WHERE a.id = :id")
+    @org.springframework.data.jpa.repository.QueryHints(
+            @javax.persistence.QueryHint(name = "org.hibernate.flushMode", value = "COMMIT"))
+    String findPersistedAppCodeById(@Param("id") Integer id);
+
     // 基石应用排除 = AppNature.isBaseApp（appKey<=100000 ∪ app_nature='BASE'）的 SQL 形态，常量拼接、语义单点见 AppNature。
     // app_nature 过渡期可空：`<> 'BASE'` 遇 NULL 求值为 NULL（非 TRUE）会整行漏掉，必须带 IS NULL 分支。
     @Query("SELECT COUNT(a.id) FROM ApplicationInfo a WHERE a.categoryId = :categoryId AND a.appKey > 100000 " +

src/main/java/com/yunhai/userbase/service/impl/ApplicationInfoService.java

@@ -145,6 +145,10 @@ public class ApplicationInfoService implements IApplicationInfoService {
      */
     @Override
     public ApplicationInfo save(ApplicationInfo info) {
+        if (info.getId() != null) {
+            requireUnchangedAppCode(applicationInfoRepository.findPersistedAppCodeById(info.getId()),
+                    info.getAppCode());
+        }
         ApplicationInfo saved = applicationInfoRepository.save(info);
         eventPublisher.publishEvent(ApplicationInfoCacheChangedEvent.upsert(this, saved));
         return saved;
@@ -199,6 +203,10 @@ public class ApplicationInfoService implements IApplicationInfoService {
         }
         ApplicationInfo entity = applicationInfoRepository.findById(id)
                 .orElseThrow(() -> new RuntimeException("应用不存在: " + id));
+        // 空值仍按既有部分提交语义处理；非空已登记标识不可真正改名。
+        if (StringUtils.isNotBlank(request.getAppCode())) {
+            requireUnchangedAppCode(entity.getAppCode(), request.getAppCode());
+        }
         if (StringUtils.isNotBlank(request.getAppCode())
                 && applicationInfoRepository.existsByAppCodeAndIdNot(request.getAppCode(), id)) {
             throw new DException("技术标识已存在");
@@ -225,6 +233,12 @@ public class ApplicationInfoService implements IApplicationInfoService {
         eventPublisher.publishEvent(ApplicationInfoCacheChangedEvent.upsert(this, saved));
     }
 
+    private static void requireUnchangedAppCode(String persisted, String proposed) {
+        if (StringUtils.isNotBlank(persisted) && !Objects.equals(persisted, proposed)) {
+            throw new DException("已登记的应用技术标识 appCode 不可修改");
+        }
+    }
+
     @Override
     @Transactional
     // AI-FIX: 删除应用同时级联删除其下全部模块（逻辑外键 appId，无物理 FK，需手动清理）；

src/test/java/com/yunhai/userbase/service/impl/ApplicationInfoAppCodeTest.java

@@ -0,0 +1,84 @@
+package com.yunhai.userbase.service.impl;
+
+import com.yunhai.userbase.entity.ApplicationInfo;
+import com.yunhai.userbase.model.application.ApplicationInfoRequest;
+import com.yunhai.userbase.repository.ApplicationInfoRepository;
+import com.yunhai.platform.utils.exception.DException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.test.util.ReflectionTestUtils;
+import java.util.Optional;
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+import static org.mockito.ArgumentMatchers.*;
+
+class ApplicationInfoAppCodeTest {
+    private ApplicationInfoService service;
+    private ApplicationInfoRepository repository;
+    private ApplicationInfo entity;
+
+    @BeforeEach
+    void setUp() {
+        service = new ApplicationInfoService();
+        repository = mock(ApplicationInfoRepository.class);
+        ReflectionTestUtils.setField(service, "applicationInfoRepository", repository);
+        ReflectionTestUtils.setField(service, "eventPublisher", mock(ApplicationEventPublisher.class));
+        entity = new ApplicationInfo();
+        entity.setId(1); entity.setAppCode("svc-hall");
+        when(repository.findById(1)).thenReturn(Optional.of(entity));
+        when(repository.save(any(ApplicationInfo.class))).thenAnswer(invocation -> invocation.getArgument(0));
+    }
+
+    private ApplicationInfoRequest request(String code) {
+        ApplicationInfoRequest r = new ApplicationInfoRequest();
+        r.setName("display-name"); r.setAppCode(code);
+        return r;
+    }
+
+    @Test
+    void editRejectsRenameBeforeMutatingEntity() {
+        for (String code : new String[]{"new-name", "SVC-HALL", "svc-hall "}) {
+            assertThrows(DException.class, () -> service.edit(1, request(code)));
+        }
+        assertEquals("svc-hall", entity.getAppCode());
+        verify(repository, never()).save(any());
+    }
+
+    @Test
+    void sameCodeOrOmittedCodeCanEditOtherFields() {
+        for (String code : new String[]{"svc-hall", null, "", "  "}) {
+            service.edit(1, request(code));
+            assertEquals("svc-hall", entity.getAppCode());
+            assertEquals("display-name", entity.getName());
+        }
+    }
+
+    @Test
+    void unregisteredCodeMayBeFilledButUniquenessStillApplies() {
+        entity.setAppCode(null);
+        when(repository.existsByAppCodeAndIdNot("taken", 1)).thenReturn(true);
+        assertThrows(DException.class, () -> service.edit(1, request("taken")));
+        service.edit(1, request("svc-hall"));
+        assertEquals("svc-hall", entity.getAppCode());
+    }
+
+    @Test
+    void genericSaveCannotRenameOrClearPersistedCode() {
+        when(repository.findPersistedAppCodeById(1)).thenReturn("svc-hall");
+        for (String code : new String[]{"new-name", null, ""}) {
+            entity.setAppCode(code);
+            assertThrows(DException.class, () -> service.save(entity));
+        }
+        entity.setAppCode("svc-hall");
+        assertSame(entity, service.save(entity));
+    }
+
+    @Test
+    void genericSaveAllowsInitialRegistration() {
+        when(repository.findPersistedAppCodeById(1)).thenReturn(null);
+        assertSame(entity, service.save(entity));
+        entity.setId(null);
+        assertSame(entity, service.save(entity));
+    }
+}