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.IntegrationTests/TestSupport/IntegrationTestCollection.cs

@@ -0,0 +1,9 @@
+using Xunit;
+
+namespace PnvPanel.IntegrationTests.TestSupport;
+
+[CollectionDefinition(Name)]
+public sealed class IntegrationTestCollection : ICollectionFixture<PnvPanelWebApplicationFactory>
+{
+    public const string Name = "Integration";
+}