Implement billing status notification and enhance user management integration

- Added `NotifyBillingStatusChangedAsync` method to `IRealtimeNotifier` for notifying clients about changes in billing status.
- Updated `BillingConfigResumer` to call the new notification method after modifying billing configurations, ensuring users receive real-time updates.
- Enhanced `ListUsersQueryHandler` to include a `BillingPendingReview` property in `UserSummaryDto`, indicating if a user has a pending payment request awaiting confirmation.
- Refactored various command handlers to utilize `AdvisoryLock` for managing concurrent requests, preventing race conditions in billing operations.
- Updated tests to cover new notification behaviors and ensure proper functionality in billing status management.

backend/tests/PnvPanel.Application.Tests/Admin/Support/ResolveTicketCommandHandlerTests.cs

@@ -1,6 +1,7 @@
 using NSubstitute;
 using PnvPanel.Application.Admin.Support;
 using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Support;
 using PnvPanel.Application.Tests.TestSupport;
 using PnvPanel.Domain.Support;
 using Xunit;
@@ -65,4 +66,34 @@ public class ResolveTicketCommandHandlerTests
         Assert.True(result.IsSuccess);
         Assert.Equal(TicketStatus.Resolved, ticket.Status);
     }
+
+    [Fact]
+    public async Task Handle_WhenRoleRequest_ReturnsOnlyBugReportCanBeResolvedDirectly()
+    {
+        // Заявку на роль/продление можно решить только через Approve/Reject — Resolve обходил бы
+        // одобрение (роль/продление так и не назначились бы), см. CLAUDE.md.
+        using var dbContext = InMemoryDbContextFactory.Create();
+        var userId = Guid.NewGuid();
+        var roleId = Guid.NewGuid();
+        var ticket = SupportTicket.CreateRoleRequestForExistingRole(userId, roleId);
+        dbContext.SupportTickets.Add(ticket);
+        await dbContext.SaveChangesAsync(CancellationToken.None);
+
+        var currentUser = FakeCurrentUser.Authenticated(Guid.NewGuid(), "admin");
+        var handler = new ResolveTicketCommandHandler(
+            dbContext,
+            _notifier,
+            _telegramNotifier,
+            currentUser
+        );
+
+        var result = await handler.Handle(
+            new ResolveTicketCommand(ticket.Id),
+            CancellationToken.None
+        );
+
+        Assert.False(result.IsSuccess);
+        Assert.Equal(SupportErrors.OnlyBugReportCanBeResolvedDirectly, result.Error);
+        Assert.Equal(TicketStatus.Open, ticket.Status);
+    }
 }