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(