Implement rate limiting and enhance authentication flow

- Added rate limiting configuration for authentication endpoints, allowing customizable request limits via environment variables.
- Updated authentication flow to utilize HttpRequest for cookie management, ensuring secure handling of refresh tokens.
- Introduced a new endpoint to retrieve user subscription details.
- Enhanced the handling of Telegram bot token validation to prevent errors with empty tokens.
- Updated the application to serialize enums as strings for better documentation and compatibility with TypeScript.
- Improved test coverage for new features and adjustments in command handlers.

backend/tests/PnvPanel.Application.Tests/Auth/LoginCommandHandlerTests.cs

@@ -20,7 +20,7 @@ public class LoginCommandHandlerTests
     {
         var userId = Guid.NewGuid();
         var authUser = new AuthenticatedUser(userId, "alice", "user");
-        var profile = new CurrentUserProfile(userId, "alice", Guid.NewGuid(), "user", IsActivated: true, IsBlocked: false, MaxConfigs: 3);
+        var profile = new CurrentUserProfile(userId, "alice", Guid.NewGuid(), "user", IsActivated: true, IsBlocked: false, MaxConfigs: 3, SubscriptionToken: "sub-token");
 
         _identityService.ValidateCredentialsAsync("alice", "P@ssw0rd", Arg.Any<CancellationToken>())
             .Returns(Result.Success(authUser));