feat: 添加期刊二维码管理功能，调整UserJournal的UserId为可空类型

1.  新增数据库脚本修改User表UserId字段为可空
2.  新增期刊二维码CRUD接口与控制器
3.  重构绑定期刊逻辑，优化重复绑定校验
4.  删除冗余的JwtHelper重载方法

QYZH.InteractiveMagazine.Models/Dto/Journal/BindJournalDto.cs

@@ -110,3 +110,117 @@ public class UserJournalQueryInput : PageQueryModel
     /// </summary>
     public string? Type { get; set; }
 }
+
+/// <summary>
+/// 生成期刊二维码输入DTO
+/// </summary>
+public class CreateUserJournalQrCodeInput
+{
+    /// <summary>
+    /// 期刊Id
+    /// </summary>
+    public long JournalId { get; set; }
+
+    /// <summary>
+    /// 关联类型: Read, Favorite, Subscribe，默认 Subscribe
+    /// </summary>
+    public string Type { get; set; } = UserJournalTypeEnum.Subscribe.ToString();
+}
+
+/// <summary>
+/// 期刊二维码查询输入DTO
+/// </summary>
+public class UserJournalQrCodeQueryInput : PageQueryModel
+{
+    /// <summary>
+    /// 期刊Id
+    /// </summary>
+    public long? JournalId { get; set; }
+
+    /// <summary>
+    /// 用户Id
+    /// </summary>
+    public long? UserId { get; set; }
+
+    /// <summary>
+    /// 是否已绑定用户
+    /// </summary>
+    public bool? IsBound { get; set; }
+
+    /// <summary>
+    /// 状态
+    /// </summary>
+    public int? Status { get; set; }
+}
+
+/// <summary>
+/// 期刊二维码输出DTO
+/// </summary>
+public class UserJournalQrCodeOutput
+{
+    /// <summary>
+    /// 二维码记录Id
+    /// </summary>
+    public long Id { get; set; }
+
+    /// <summary>
+    /// 期刊Id
+    /// </summary>
+    public long JournalId { get; set; }
+
+    /// <summary>
+    /// 期刊名称
+    /// </summary>
+    public string JournalName { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 用户Id
+    /// </summary>
+    public long? UserId { get; set; }
+
+    /// <summary>
+    /// 用户昵称
+    /// </summary>
+    public string? UserName { get; set; }
+
+    /// <summary>
+    /// 关联类型
+    /// </summary>
+    public string Type { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 状态
+    /// </summary>
+    public string Status { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 是否已绑定用户
+    /// </summary>
+    public bool IsBound { get; set; }
+
+    /// <summary>
+    /// 二维码内容
+    /// </summary>
+    public string QrCodeContent { get; set; } = string.Empty;
+
+    /// <summary>
+    /// 创建时间
+    /// </summary>
+    public DateTime CreatedAt { get; set; }
+
+    /// <summary>
+    /// 绑定时间
+    /// </summary>
+    public DateTime? BoundAt { get; set; }
+}
+
+/// <summary>
+/// 删除期刊二维码输入DTO
+/// </summary>
+public class DeleteUserJournalQrCodeInput
+{
+    /// <summary>
+    /// 二维码记录Id列表
+    /// </summary>
+    public List<long> Ids { get; set; } = [];
+}