Implement extension request and gift functionalities in billing system

- Added new endpoints for creating and managing extension requests, allowing users to request billing period extensions.
- Implemented admin approval processes for extension requests via Telegram, including inline buttons for approval and rejection.
- Introduced a gifting feature for admins to grant additional billing days directly to users without a request.
- Updated the support ticket model to accommodate extension requests and their associated properties.
- Enhanced the Telegram notifier to inform admins of new extension requests and notify users of approval or rejection.
- Updated frontend components to support the new extension request and gifting functionalities, including user interfaces for managing these features.
- Revised API documentation to reflect the new endpoints and their usage in the billing context.

backend/src/PnvPanel.Application/Admin/Billing/ConfirmPaymentRequestCommandHandler.cs

@@ -7,7 +7,6 @@ using PnvPanel.Application.Common.Messaging;
 using PnvPanel.Application.Common.Models;
 using PnvPanel.Domain.Audit;
 using PnvPanel.Domain.Billing;
-using PnvPanel.Domain.Configs;
 
 namespace PnvPanel.Application.Admin.Billing;
 
@@ -65,64 +64,15 @@ public sealed class ConfirmPaymentRequestCommandHandler(
 
         request.Confirm(adminId);
 
-        var configs = await dbContext
-            .VpnConfigs.Where(c =>
-                c.UserId == request.UserId
-                && (c.Status == ConfigStatus.Active || c.Status == ConfigStatus.Expired)
-            )
-            .ToListAsync(cancellationToken);
-
-        foreach (var config in configs)
-        {
-            if (config.Status == ConfigStatus.Expired)
-            {
-                var inbound = await dbContext
-                    .Inbounds.AsNoTracking()
-                    .FirstOrDefaultAsync(i => i.Id == config.InboundId, cancellationToken);
-                var node = inbound is null
-                    ? null
-                    : await dbContext
-                        .Nodes.AsNoTracking()
-                        .FirstOrDefaultAsync(n => n.Id == inbound.NodeId, cancellationToken);
-
-                if (inbound is not null && node is not null)
-                {
-                    var updateResult = await gateway.UpdateClientAsync(
-                        node,
-                        inbound.RemoteInboundId,
-                        config.ClientExternalId,
-                        config.Protocol,
-                        config.Label ?? config.ClientEmail,
-                        enable: true,
-                        cancellationToken
-                    );
-
-                    if (!updateResult.IsSuccess)
-                    {
-                        // Нода недоступна — не трогаем локальный статус, подхватится следующим
-                        // подтверждением/циклом BillingService (идемпотентно).
-                        logger.LogWarning(
-                            "Failed to enable client for config {ConfigId} on node {NodeId} while confirming payment {RequestId}: {Error}",
-                            config.Id,
-                            node.Id,
-                            request.Id,
-                            updateResult.Error
-                        );
-                        continue;
-                    }
-                }
-
-                config.Resume();
-                await notifier.NotifyConfigStatusChangedAsync(
-                    config.UserId,
-                    config.Id,
-                    config.Status,
-                    cancellationToken
-                );
-            }
-
-            config.SetBillingExpiry(newPaidUntil);
-        }
+        await BillingConfigResumer.ResumeConfigsAsync(
+            dbContext,
+            gateway,
+            notifier,
+            logger,
+            request.UserId,
+            newPaidUntil,
+            cancellationToken
+        );
 
         dbContext.AuditLogs.Add(
             AuditLog.Create(

backend/src/PnvPanel.Application/Admin/Billing/GrantBillingGiftCommand.cs

@@ -0,0 +1,8 @@
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Admin.Billing;
+
+/// <summary>Админ дарит пользователю N дней подписки — продлевает BillingPaidUntil от
+/// max(текущий, сейчас), возвращает приостановленные конфиги, шлёт уведомление пользователю.</summary>
+public sealed record GrantBillingGiftCommand(Guid UserId, int Days) : ICommand<Result>;

backend/src/PnvPanel.Application/Admin/Billing/GrantBillingGiftCommandHandler.cs

@@ -0,0 +1,76 @@
+using Microsoft.Extensions.Logging;
+using PnvPanel.Application.Admin.Users;
+using PnvPanel.Application.Auth;
+using PnvPanel.Application.Billing;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+using PnvPanel.Domain.Audit;
+
+namespace PnvPanel.Application.Admin.Billing;
+
+public sealed class GrantBillingGiftCommandHandler(
+    IAppDbContext dbContext,
+    IIdentityService identityService,
+    IXuiPanelGateway gateway,
+    IRealtimeNotifier notifier,
+    ITelegramNotifier telegramNotifier,
+    ICurrentUser currentUser,
+    ILogger<GrantBillingGiftCommandHandler> logger
+) : ICommandHandler<GrantBillingGiftCommand, Result>
+{
+    public async Task<Result> Handle(GrantBillingGiftCommand command, CancellationToken cancellationToken)
+    {
+        if (currentUser.UserId is not { } adminId)
+            return Result.Failure(AuthErrors.Unauthorized);
+
+        var profile = await identityService.GetProfileAsync(command.UserId, cancellationToken);
+        if (profile is null)
+            return Result.Failure(UserErrors.NotFound);
+
+        if (!profile.BillingEnabled)
+            return Result.Failure(BillingErrors.NotEnabled);
+
+        var now = DateTimeOffset.UtcNow;
+        var baseline = profile.BillingPaidUntil is { } paidUntil && paidUntil > now ? paidUntil : now;
+        var newPaidUntil = baseline.AddDays(command.Days);
+
+        var extendResult = await identityService.ExtendBillingPaidUntilAsync(
+            command.UserId,
+            newPaidUntil,
+            cancellationToken
+        );
+        if (!extendResult.IsSuccess)
+            return extendResult;
+
+        await BillingConfigResumer.ResumeConfigsAsync(
+            dbContext,
+            gateway,
+            notifier,
+            logger,
+            command.UserId,
+            newPaidUntil,
+            cancellationToken
+        );
+
+        dbContext.AuditLogs.Add(
+            AuditLog.Create(
+                adminId,
+                "BillingGiftGranted",
+                "User",
+                command.UserId.ToString(),
+                metadata: $"{{\"days\":{command.Days}}}",
+                AuditSource.Web
+            )
+        );
+
+        await telegramNotifier.NotifyUserAsync(
+            command.UserId,
+            $"🎁 Вам подарено {command.Days} дн. подписки! Доступ продлён до {newPaidUntil:dd.MM.yyyy}.",
+            "/billing",
+            cancellationToken
+        );
+
+        return Result.Success();
+    }
+}

backend/src/PnvPanel.Application/Admin/Billing/GrantBillingGiftCommandValidator.cs

@@ -0,0 +1,11 @@
+using FluentValidation;
+
+namespace PnvPanel.Application.Admin.Billing;
+
+public sealed class GrantBillingGiftCommandValidator : AbstractValidator<GrantBillingGiftCommand>
+{
+    public GrantBillingGiftCommandValidator()
+    {
+        RuleFor(x => x.Days).GreaterThan(0).LessThanOrEqualTo(365);
+    }
+}