Add Telegram bot integration and enhance user management features

- Introduced Telegram.Bot package for bot functionality.
- Updated user management to include Telegram linking and blocking features.
- Enhanced activation request handling with notifications via Telegram.
- Added new database entities for Telegram link tokens and login requests.
- Implemented traffic synchronization for client stats in the XuiPanelGateway.
- Updated application structure to support new test projects and improved dependency injection for Telegram services.

backend/tests/PnvPanel.Application.Tests/Telegram/CreateLinkTokenCommandHandlerTests.cs

@@ -0,0 +1,40 @@
+using PnvPanel.Application.Auth;
+using PnvPanel.Application.Telegram;
+using PnvPanel.Application.Tests.TestSupport;
+using Xunit;
+
+namespace PnvPanel.Application.Tests.Telegram;
+
+public class CreateLinkTokenCommandHandlerTests
+{
+    [Fact]
+    public async Task Handle_WhenAuthenticated_CreatesTokenAndAddsToDbContext()
+    {
+        using var dbContext = InMemoryDbContextFactory.Create();
+        var userId = Guid.NewGuid();
+
+        var handler = new CreateLinkTokenCommandHandler(dbContext, FakeCurrentUser.Authenticated(userId));
+
+        var result = await handler.Handle(new CreateLinkTokenCommand(), CancellationToken.None);
+
+        Assert.True(result.IsSuccess);
+        Assert.False(string.IsNullOrEmpty(result.Value.Token));
+        Assert.True(result.Value.ExpiresAt > DateTimeOffset.UtcNow);
+        Assert.Single(dbContext.TelegramLinkTokens.Local);
+        Assert.Equal(userId, dbContext.TelegramLinkTokens.Local.Single().UserId);
+    }
+
+    [Fact]
+    public async Task Handle_WhenNotAuthenticated_ReturnsUnauthorized()
+    {
+        using var dbContext = InMemoryDbContextFactory.Create();
+
+        var handler = new CreateLinkTokenCommandHandler(dbContext, FakeCurrentUser.Anonymous());
+
+        var result = await handler.Handle(new CreateLinkTokenCommand(), CancellationToken.None);
+
+        Assert.False(result.IsSuccess);
+        Assert.Equal(AuthErrors.Unauthorized, result.Error);
+        Assert.Empty(dbContext.TelegramLinkTokens.Local);
+    }
+}