Implement billing functionality and enhance role management

- Introduced billing capabilities, allowing users to request payments for subscription periods (3/6/12 months) with admin approval via Telegram.
- Updated role management to include a `BillingEnabled` property, preventing billing for admin roles.
- Enhanced the `CreateRoleCommand` and `UpdateRoleCommand` to accept billing parameters, ensuring proper handling during role creation and updates.
- Added new endpoints for billing management and integrated billing checks into VPN config creation to enforce payment requirements.
- Updated related services, models, and tests to support the new billing features, ensuring comprehensive coverage and functionality.
- Enhanced documentation to reflect the new billing processes and role management changes.

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

@@ -1,5 +1,6 @@
 using Microsoft.Extensions.Options;
 using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Domain.Billing;
 using PnvPanel.Domain.Support;
 using PnvPanel.Infrastructure.Telegram;
 using Telegram.Bot;
@@ -225,6 +226,56 @@ internal sealed class TelegramNotifier(
         }
     }
 
+    public async Task NotifyAdminsPaymentRequestedAsync(
+        Guid requestId,
+        string userName,
+        PaymentPeriod period,
+        int amount,
+        CancellationToken cancellationToken
+    )
+    {
+        if (string.IsNullOrWhiteSpace(options.Value.BotToken))
+            return;
+
+        var text =
+            $"💰 <b>{Escape(userName)}</b> заявляет об оплате за {PeriodLabel(period)} — {amount} ₽\nПроверьте поступление и подтвердите.";
+
+        var keyboard = new InlineKeyboardMarkup(
+            new[]
+            {
+                InlineKeyboardButton.WithCallbackData("✅ Подтвердить", $"pay:approve:{requestId}"),
+                InlineKeyboardButton.WithCallbackData("❌ Отклонить", $"pay:reject:{requestId}"),
+            }
+        );
+
+        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.
+            }
+        }
+    }
+
+    private static string PeriodLabel(PaymentPeriod period) =>
+        period switch
+        {
+            PaymentPeriod.Quarter => "3 месяца",
+            PaymentPeriod.HalfYear => "полгода",
+            PaymentPeriod.Year => "год",
+            _ => period.ToString(),
+        };
+
     public async Task NotifyUserAsync(
         Guid userId,
         string message,