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.Api/Endpoints/AdminBillingEndpoints.cs

@@ -26,6 +26,7 @@ public static class AdminBillingEndpoints
         admin
             .MapPost("/requests/{id:guid}/reject", RejectRequest)
             .Produces(StatusCodes.Status204NoContent);
+        admin.MapPost("/gift", GrantGift).Produces(StatusCodes.Status204NoContent);
 
         return app;
     }
@@ -80,6 +81,19 @@ public static class AdminBillingEndpoints
         );
         return result.ToHttpResult();
     }
+
+    private static async Task<IResult> GrantGift(
+        GrantGiftBody body,
+        ISender sender,
+        CancellationToken cancellationToken
+    )
+    {
+        var result = await sender.Send(
+            new GrantBillingGiftCommand(body.UserId, body.Days),
+            cancellationToken
+        );
+        return result.ToHttpResult();
+    }
 }
 
 public sealed record ListPaymentRequestsRequest(
@@ -89,3 +103,5 @@ public sealed record ListPaymentRequestsRequest(
 );
 
 public sealed record RejectPaymentRequestBody(string? Reason);
+
+public sealed record GrantGiftBody(Guid UserId, int Days);

backend/src/PnvPanel.Api/Endpoints/AdminSupportEndpoints.cs

@@ -33,6 +33,12 @@ public static class AdminSupportEndpoints
         admin
             .MapPost("/tickets/{id:guid}/reject", RejectRoleRequest)
             .Produces(StatusCodes.Status204NoContent);
+        admin
+            .MapPost("/tickets/{id:guid}/approve-extension", ApproveExtensionRequest)
+            .Produces(StatusCodes.Status204NoContent);
+        admin
+            .MapPost("/tickets/{id:guid}/reject-extension", RejectExtensionRequest)
+            .Produces(StatusCodes.Status204NoContent);
 
         return app;
     }
@@ -119,6 +125,32 @@ public static class AdminSupportEndpoints
         );
         return result.ToHttpResult();
     }
+
+    private static async Task<IResult> ApproveExtensionRequest(
+        Guid id,
+        ISender sender,
+        CancellationToken cancellationToken
+    )
+    {
+        var result = await sender.Send(new ApproveExtensionRequestCommand(id), cancellationToken);
+        return result.ToHttpResult();
+    }
+
+    private static async Task<IResult> RejectExtensionRequest(
+        Guid id,
+        RejectExtensionRequestBody body,
+        ISender sender,
+        CancellationToken cancellationToken
+    )
+    {
+        var result = await sender.Send(
+            new RejectExtensionRequestCommand(id, body.Reason),
+            cancellationToken
+        );
+        return result.ToHttpResult();
+    }
 }
 
 public sealed record RejectRoleRequestBody(string? Reason);
+
+public sealed record RejectExtensionRequestBody(string? Reason);

backend/src/PnvPanel.Api/Endpoints/SupportEndpoints.cs

@@ -6,6 +6,7 @@ using PnvPanel.Application.Common.Models;
 using PnvPanel.Application.Support;
 using PnvPanel.Application.Support.AddComment;
 using PnvPanel.Application.Support.CreateBugReport;
+using PnvPanel.Application.Support.CreateExtensionRequest;
 using PnvPanel.Application.Support.CreateRoleRequest;
 using PnvPanel.Application.Support.GetAttachment;
 using PnvPanel.Application.Support.GetSupportPricing;
@@ -30,6 +31,9 @@ public static class SupportEndpoints
             .DisableAntiforgery()
             .Produces<TicketDetailDto>();
         group.MapPost("/tickets/role-requests", CreateRoleRequest).Produces<TicketDetailDto>();
+        group
+            .MapPost("/tickets/extension-requests", CreateExtensionRequest)
+            .Produces<TicketDetailDto>();
         group.MapGet("/tickets", ListMyTickets).Produces<PagedList<TicketSummaryDto>>();
         group.MapGet("/tickets/{id:guid}", GetTicket).Produces<TicketDetailDto>();
         group
@@ -89,6 +93,17 @@ public static class SupportEndpoints
         return result.ToHttpResult();
     }
 
+    private static async Task<IResult> CreateExtensionRequest(
+        CreateExtensionRequestBody body,
+        ISender sender,
+        CancellationToken cancellationToken
+    )
+    {
+        var command = new CreateExtensionRequestTicketCommand(body.RequestedDays, body.Justification);
+        var result = await sender.Send(command, cancellationToken);
+        return result.ToHttpResult();
+    }
+
     private static async Task<IResult> ListMyTickets(
         [AsParameters] ListTicketsRequest request,
         ISender sender,
@@ -175,6 +190,8 @@ public sealed record CreateRoleRequestBody(
     string Justification
 );
 
+public sealed record CreateExtensionRequestBody(int RequestedDays, string Justification);
+
 public sealed record ListTicketsRequest(
     TicketType? Type,
     TicketStatus? Status,

backend/src/PnvPanel.Api/Telegram/PnvBotUpdateHandler.cs

@@ -489,6 +489,55 @@ public sealed class PnvBotUpdateHandler(
 
                 break;
             }
+            case "erq":
+            {
+                if (!await TrySetAdminCurrentUserAsync(services, fromId, cancellationToken))
+                {
+                    await botClient.AnswerCallbackQuery(
+                        callback.Id,
+                        "Недостаточно прав.",
+                        cancellationToken: cancellationToken
+                    );
+                    return;
+                }
+
+                var result =
+                    parts[1] == "approve"
+                        ? await sender.Send(
+                            new ApproveExtensionRequestCommand(requestId),
+                            cancellationToken
+                        )
+                        : await sender.Send(
+                            new RejectExtensionRequestCommand(requestId, Reason: null),
+                            cancellationToken
+                        );
+
+                await botClient.AnswerCallbackQuery(
+                    callback.Id,
+                    result.IsSuccess ? "Готово" : result.Error.Message,
+                    cancellationToken: cancellationToken
+                );
+                if (callback.Message is not null)
+                {
+                    var statusText = result.IsSuccess
+                        ? (
+                            parts[1] == "approve"
+                                ? "✅ Заявка на продление одобрена."
+                                : "❌ Заявка отклонена."
+                        )
+                        : $"⚠️ {result.Error.Message}";
+                    var text = $"{Escape(callback.Message.Text ?? "")}\n\n{statusText}";
+                    await botClient.EditMessageText(
+                        chatId.Value,
+                        callback.Message.Id,
+                        text,
+                        parseMode: ParseMode.Html,
+                        cancellationToken: cancellationToken
+                    );
+                }
+
+                break;
+            }
             case "pay":
             {
                 if (!await TrySetAdminCurrentUserAsync(services, fromId, cancellationToken))

backend/src/PnvPanel.Api/Telegram/TelegramNotifier.cs

@@ -144,6 +144,47 @@ internal sealed class TelegramNotifier(
         }
     }
 
+    public async Task NotifyAdminsExtensionRequestCreatedAsync(
+        Guid ticketId,
+        string userName,
+        int requestedDays,
+        string justification,
+        CancellationToken cancellationToken
+    )
+    {
+        if (string.IsNullOrWhiteSpace(options.Value.BotToken))
+            return;
+
+        var text =
+            $"🆕 Заявка на продление от <b>{Escape(userName)}</b> — {requestedDays} дн.\nОбоснование: {Escape(justification)}";
+
+        var keyboard = new InlineKeyboardMarkup(
+            new[]
+            {
+                InlineKeyboardButton.WithCallbackData("✅ Одобрить", $"erq:approve:{ticketId}"),
+                InlineKeyboardButton.WithCallbackData("❌ Отклонить", $"erq:reject:{ticketId}"),
+            }
+        );
+
+        foreach (var adminId in options.Value.ParseAdminTelegramUserIds())
+        {
+            try
+            {
+                await botClient.SendMessage(
+                    adminId,
+                    text,
+                    parseMode: ParseMode.Html,
+                    replyMarkup: keyboard,
+                    cancellationToken: cancellationToken
+                );
+            }
+            catch
+            {
+                // Админ мог не запускать бота (нет чата с ботом) — пропускаем, не валим команду.
+            }
+        }
+    }
+
     public async Task NotifyAdminsTicketReopenedAsync(
         Guid ticketId,
         string userName,