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/src/PnvPanel.Application/Configs/GetMySubscription/GetMySubscriptionQuery.cs

@@ -0,0 +1,9 @@
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Configs.GetMySubscription;
+
+public sealed record GetMySubscriptionQuery : IQuery<Result<MySubscriptionDto>>;
+
+/// <summary>SubscriptionToken — Api-слой строит из него абсолютный URL (знает scheme/host запроса), см. GetConfigLinkQuery.</summary>
+public sealed record MySubscriptionDto(string SubscriptionToken);

backend/src/PnvPanel.Application/Configs/GetMySubscription/GetMySubscriptionQueryHandler.cs

@@ -0,0 +1,22 @@
+using PnvPanel.Application.Auth;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Configs.GetMySubscription;
+
+public sealed class GetMySubscriptionQueryHandler(IIdentityService identityService, ICurrentUser currentUser)
+    : IQueryHandler<GetMySubscriptionQuery, Result<MySubscriptionDto>>
+{
+    public async Task<Result<MySubscriptionDto>> Handle(GetMySubscriptionQuery query, CancellationToken cancellationToken)
+    {
+        if (currentUser.UserId is not { } userId)
+            return Result.Failure<MySubscriptionDto>(AuthErrors.Unauthorized);
+
+        var profile = await identityService.GetProfileAsync(userId, cancellationToken);
+        if (profile is null)
+            return Result.Failure<MySubscriptionDto>(AuthErrors.Unauthorized);
+
+        return Result.Success(new MySubscriptionDto(profile.SubscriptionToken));
+    }
+}