Add Telegram notification for news publication to users

- Implemented NotifyUsersNewsPublishedAsync method in TelegramNotifier to send notifications to activated Telegram users when a news post is published.
- Updated CreatePostCommandHandler to invoke the new Telegram notification method after creating a news post.
- Enhanced IIdentityService to retrieve activated linked Telegram user IDs for notifications.
- Updated ITelegramNotifier interface to include the new notification method documentation.

backend/src/PnvPanel.Application/Admin/News/CreatePostCommandHandler.cs

@@ -6,7 +6,7 @@ using PnvPanel.Domain.News;
 
 namespace PnvPanel.Application.Admin.News;
 
-public sealed class CreatePostCommandHandler(IAppDbContext dbContext, IRealtimeNotifier notifier)
+public sealed class CreatePostCommandHandler(IAppDbContext dbContext, IRealtimeNotifier notifier, ITelegramNotifier telegramNotifier)
     : ICommandHandler<CreatePostCommand, Result<NewsPostDto>>
 {
     public async Task<Result<NewsPostDto>> Handle(CreatePostCommand command, CancellationToken cancellationToken)
@@ -15,6 +15,7 @@ public sealed class CreatePostCommandHandler(IAppDbContext dbContext, IRealtimeN
         dbContext.NewsPosts.Add(post);
 
         await notifier.NotifyNewsPublishedAsync(post.Id, post.Title, post.CreatedAt, cancellationToken);
+        await telegramNotifier.NotifyUsersNewsPublishedAsync(post.Title, cancellationToken);
 
         return Result.Success(NewsPostDto.FromDomain(post));
     }

backend/src/PnvPanel.Application/Common/Interfaces/IIdentityService.cs

@@ -60,4 +60,8 @@ public interface IIdentityService
     Task<Guid?> FindUserIdByTelegramUserIdAsync(long telegramUserId, CancellationToken cancellationToken);
 
     Task<TelegramLinkInfo> GetTelegramLinkInfoAsync(Guid userId, CancellationToken cancellationToken);
+
+    /// <summary>Telegram ID активных (активированных, не заблокированных) пользователей с привязкой —
+    /// для рассылки уведомлений вроде публикации новости.</summary>
+    Task<IReadOnlyCollection<long>> GetActivatedLinkedTelegramUserIdsAsync(CancellationToken cancellationToken);
 }

backend/src/PnvPanel.Application/Common/Interfaces/ITelegramNotifier.cs

@@ -21,4 +21,8 @@ public interface ITelegramNotifier
     /// <summary>Заявка на роль — инлайн-кнопки «Одобрить/Отклонить», решается полностью в Telegram.</summary>
     Task NotifyAdminsRoleRequestCreatedAsync(
         Guid ticketId, string userName, string roleDescription, string justification, CancellationToken cancellationToken);
+
+    /// <summary>Рассылка о публикации новости всем активированным пользователям с привязанным Telegram
+    /// (кнопка-ссылка на сайт, где новость показана целиком).</summary>
+    Task NotifyUsersNewsPublishedAsync(string title, CancellationToken cancellationToken);
 }