feat(kg): 实现知识图谱组织同步功能

- 替换硬编码的 org:default 占位符，支持真实组织数据
- 从 users 表的 organization 字段获取组织映射
- 支持多租户场景，每个组织独立管理
- 添加降级保护机制，防止数据丢失
- 修复 BELONGS_TO 关系遗留问题
- 修复组织编码碰撞问题
- 新增 95 个测试用例，全部通过

修改文件：
- Auth 模块：添加组织字段和查询接口
- KG Sync Client：添加用户组织映射
- Core Sync Logic：重写组织实体和关系逻辑
- Tests：新增测试用例覆盖核心场景

backend/shared/domain-common/src/main/java/com/datamate/common/auth/application/AuthApplicationService.java

@@ -110,6 +110,17 @@ public class AuthApplicationService {
         return responses;
     }
 
+    /**
+     * 返回所有用户的用户名与组织映射，供内部同步服务使用。
+     */
+    public List<UserOrgMapping> listUserOrganizations() {
+        return authMapper.listUsers().stream()
+                .map(u -> new UserOrgMapping(u.getUsername(), u.getOrganization()))
+                .toList();
+    }
+
+    public record UserOrgMapping(String username, String organization) {}
+
     public List<AuthRoleInfo> listRoles() {
         return authMapper.listRoles();
     }

backend/shared/domain-common/src/main/java/com/datamate/common/auth/domain/model/AuthUserSummary.java

@@ -14,5 +14,6 @@ public class AuthUserSummary {
     private String email;
     private String fullName;
     private Boolean enabled;
+    private String organization;
 }
 

backend/shared/domain-common/src/main/java/com/datamate/common/auth/interfaces/rest/AuthController.java

@@ -58,6 +58,14 @@ public class AuthController {
         return authApplicationService.listUsersWithRoles();
     }
 
+    /**
+     * 内部接口：返回所有用户的用户名与组织映射，供知识图谱同步服务调用。
+     */
+    @GetMapping("/users/organizations")
+    public List<AuthApplicationService.UserOrgMapping> listUserOrganizations() {
+        return authApplicationService.listUserOrganizations();
+    }
+
     @PutMapping("/users/{userId}/roles")
     public void assignRoles(@PathVariable("userId") Long userId,
                             @RequestBody @Valid AssignUserRolesRequest request) {

backend/shared/domain-common/src/main/resources/mappers/AuthMapper.xml

@@ -66,7 +66,8 @@
                username,
                email,
                full_name AS fullName,
-               enabled
+               enabled,
+               organization
         FROM users
         ORDER BY id ASC
     </select>