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/RefreshCommandHandlerTests.cs

@@ -19,7 +19,7 @@ public class RefreshCommandHandlerTests
     public async Task Handle_WithValidToken_RotatesAndReturnsNewAuthResult()
     {
         var userId = Guid.NewGuid();
-        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");
         var rotated = new RotatedRefreshToken(userId, "new-refresh-token", DateTimeOffset.UtcNow.AddDays(30));
 
         _refreshTokenService.RotateAsync("old-token", Arg.Any<CancellationToken>()).Returns(Result.Success(rotated));