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/TestSupport/FakeCurrentUser.cs

@@ -0,0 +1,17 @@
+using PnvPanel.Application.Common.Interfaces;
+
+namespace PnvPanel.Application.Tests.TestSupport;
+
+public sealed class FakeCurrentUser : ICurrentUser
+{
+    public Guid? UserId { get; set; }
+
+    public string? UserName { get; set; }
+
+    public bool IsAuthenticated => UserId is not null;
+
+    public static FakeCurrentUser Authenticated(Guid userId, string userName = "testuser")
+        => new() { UserId = userId, UserName = userName };
+
+    public static FakeCurrentUser Anonymous() => new();
+}