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.Api/Telegram/TelegramNotifier.cs

@@ -97,6 +97,35 @@ internal sealed class TelegramNotifier(ITelegramBotClient botClient, IIdentitySe
         }
     }
 
+    public async Task NotifyUsersNewsPublishedAsync(string title, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(options.Value.BotToken))
+            return;
+
+        var text = $"📰 Новая новость: <b>{Escape(title)}</b>";
+
+        InlineKeyboardMarkup? keyboard = null;
+        if (!string.IsNullOrWhiteSpace(options.Value.PublicSiteUrl))
+        {
+            var url = $"{options.Value.PublicSiteUrl.TrimEnd('/')}/news";
+            keyboard = new InlineKeyboardMarkup(new[] { InlineKeyboardButton.WithUrl("🌐 Открыть на сайте", url) });
+        }
+
+        var telegramUserIds = await identityService.GetActivatedLinkedTelegramUserIdsAsync(cancellationToken);
+        foreach (var telegramUserId in telegramUserIds)
+        {
+            try
+            {
+                await botClient.SendMessage(
+                    telegramUserId, text, parseMode: ParseMode.Html, replyMarkup: keyboard, cancellationToken: cancellationToken);
+            }
+            catch
+            {
+                // Пользователь мог заблокировать бота — не критично, продолжаем рассылку остальным.
+            }
+        }
+    }
+
     public async Task NotifyUserAsync(Guid userId, string message, CancellationToken cancellationToken)
     {
         if (string.IsNullOrWhiteSpace(options.Value.BotToken))