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));
     }