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/tests/PnvPanel.Application.Tests/Support/ReopenTicketCommandHandlerTests.cs

@@ -1,3 +1,5 @@
+using NSubstitute;
+using PnvPanel.Application.Common.Interfaces;
 using PnvPanel.Application.Support;
 using PnvPanel.Application.Support.Reopen;
 using PnvPanel.Application.Tests.TestSupport;
@@ -8,6 +10,8 @@ namespace PnvPanel.Application.Tests.Support;
 
 public class ReopenTicketCommandHandlerTests
 {
+    private readonly ITelegramNotifier _telegramNotifier = Substitute.For<ITelegramNotifier>();
+
     [Fact]
     public async Task Handle_WhenResolved_SetsOpen()
     {
@@ -19,12 +23,14 @@ public class ReopenTicketCommandHandlerTests
         await dbContext.SaveChangesAsync(CancellationToken.None);
 
         var currentUser = FakeCurrentUser.Authenticated(userId);
-        var handler = new ReopenTicketCommandHandler(dbContext, currentUser);
+        var handler = new ReopenTicketCommandHandler(dbContext, _telegramNotifier, currentUser);
 
         var result = await handler.Handle(new ReopenTicketCommand(ticket.Id), CancellationToken.None);
 
         Assert.True(result.IsSuccess);
         Assert.Equal(TicketStatus.Open, ticket.Status);
+        await _telegramNotifier.Received(1).NotifyAdminsTicketReopenedAsync(
+            ticket.Id, Arg.Any<string>(), TicketType.BugReport, Arg.Any<CancellationToken>());
     }
 
     [Fact]
@@ -37,7 +43,7 @@ public class ReopenTicketCommandHandlerTests
         await dbContext.SaveChangesAsync(CancellationToken.None);
 
         var currentUser = FakeCurrentUser.Authenticated(userId);
-        var handler = new ReopenTicketCommandHandler(dbContext, currentUser);
+        var handler = new ReopenTicketCommandHandler(dbContext, _telegramNotifier, currentUser);
 
         var result = await handler.Handle(new ReopenTicketCommand(ticket.Id), CancellationToken.None);
 
@@ -55,7 +61,7 @@ public class ReopenTicketCommandHandlerTests
         await dbContext.SaveChangesAsync(CancellationToken.None);
 
         var currentUser = FakeCurrentUser.Authenticated(Guid.NewGuid());
-        var handler = new ReopenTicketCommandHandler(dbContext, currentUser);
+        var handler = new ReopenTicketCommandHandler(dbContext, _telegramNotifier, currentUser);
 
         var result = await handler.Handle(new ReopenTicketCommand(ticket.Id), CancellationToken.None);