Add notification for ticket reopening to Telegram admins

- Implemented NotifyAdminsTicketReopenedAsync method in TelegramNotifier to notify admins when a ticket is reopened, including a link to the ticket on the public site.
- Updated ITelegramNotifier interface to include the new notification method.
- Modified ReopenTicketCommandHandler to invoke the new notification method after a ticket is reopened.
- Enhanced unit tests for ReopenTicketCommandHandler to verify the notification functionality.

backend/src/PnvPanel.Api/Telegram/TelegramNotifier.cs

@@ -1,5 +1,6 @@
 using Microsoft.Extensions.Options;
 using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Domain.Support;
 using PnvPanel.Infrastructure.Telegram;
 using Telegram.Bot;
 using Telegram.Bot.Types.Enums;
@@ -97,6 +98,35 @@ internal sealed class TelegramNotifier(ITelegramBotClient botClient, IIdentitySe
         }
     }
 
+    public async Task NotifyAdminsTicketReopenedAsync(Guid ticketId, string userName, TicketType type, CancellationToken cancellationToken)
+    {
+        if (string.IsNullOrWhiteSpace(options.Value.BotToken))
+            return;
+
+        var typeLabel = type == TicketType.RoleRequest ? "заявка на роль" : "баг/предложение";
+        var text = $"🔓 Тикет от <b>{Escape(userName)}</b> переоткрыт ({typeLabel})";
+
+        InlineKeyboardMarkup? keyboard = null;
+        if (!string.IsNullOrWhiteSpace(options.Value.PublicSiteUrl))
+        {
+            var url = $"{options.Value.PublicSiteUrl.TrimEnd('/')}/admin/support?ticket={ticketId}";
+            keyboard = new InlineKeyboardMarkup(new[] { InlineKeyboardButton.WithUrl("🌐 Открыть на сайте", url) });
+        }
+
+        foreach (var adminId in options.Value.ParseAdminTelegramUserIds())
+        {
+            try
+            {
+                await botClient.SendMessage(
+                    adminId, text, parseMode: ParseMode.Html, replyMarkup: keyboard, cancellationToken: cancellationToken);
+            }
+            catch
+            {
+                // Админ мог не запускать бота (нет чата с ботом) — пропускаем, не валим команду.
+            }
+        }
+    }
+
     public async Task NotifyUsersNewsPublishedAsync(string title, CancellationToken cancellationToken)
     {
         if (string.IsNullOrWhiteSpace(options.Value.BotToken))