feat: 新增配额包/支付相关实体与迁移

App：新增 operation_logs/quota_packages/tenant_payments/tenant_quota_package_purchases 表

Identity：修正 Avatar 字段类型（varchar(256)->text），保持现有数据不变

src/Domain/TakeoutSaaS.Domain/Tenants/Repositories/ITenantRepository.cs

@@ -16,6 +16,14 @@ public interface ITenantRepository
     /// <returns>租户实体，未找到返回 null。</returns>
     Task<Tenant?> FindByIdAsync(long tenantId, CancellationToken cancellationToken = default);
 
+    /// <summary>
+    /// 批量获取租户。
+    /// </summary>
+    /// <param name="tenantIds">租户 ID 列表。</param>
+    /// <param name="cancellationToken">取消标记。</param>
+    /// <returns>租户列表（仅返回找到的租户）。</returns>
+    Task<IReadOnlyList<Tenant>> FindByIdsAsync(IReadOnlyCollection<long> tenantIds, CancellationToken cancellationToken = default);
+
     /// <summary>
     /// 按状态与关键词查询租户列表。
     /// </summary>