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/HttpClientJsonExtensions.cs

@@ -0,0 +1,19 @@
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json;
+
+namespace PnvPanel.IntegrationTests.TestSupport;
+
+public static class HttpClientJsonExtensions
+{
+    public static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web);
+
+    public static void UseBearerToken(this HttpClient client, string accessToken)
+        => client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
+
+    public static async Task<T?> ReadAsAsync<T>(this HttpResponseMessage response)
+        => await response.Content.ReadFromJsonAsync<T>(JsonOptions);
+
+    public static Task<HttpResponseMessage> PostJsonAsync(this HttpClient client, string url, object body)
+        => client.PostAsJsonAsync(url, body, JsonOptions);
+}