fix(admin): createUser — unique openid + try-catch exception handling

cfc-backend/src/main/java/com/etotem/cfc/controller/admin/AdminController.java

@@ -96,12 +96,16 @@ public class AdminController {
         user.setRole(role != null ? role : "parent");
         user.setRealName(realName);
         user.setPassword("");
-        user.setOpenid("");          // 非微信用户，默认空值
+        user.setOpenid("admin_" + System.currentTimeMillis());  // 唯一值避免索引冲突
         user.setFamilyId(0L);        // 尚未加入家庭
         user.setCreatedAt(new Date());
         user.setUpdatedAt(new Date());
         
-        userMapper.insert(user);
+        try {
+            userMapper.insert(user);
+        } catch (Exception e) {
+            return Result.error("创建用户失败: " + e.getMessage());
+        }
         return Result.success(user);
     }