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/Configs/Rotate/RotateVpnConfigCommandHandlerTests.cs

@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using NSubstitute;
 using PnvPanel.Application.Auth;
 using PnvPanel.Application.Common.Interfaces;
@@ -5,13 +7,53 @@ using PnvPanel.Application.Common.Models;
 using PnvPanel.Application.Configs;
 using PnvPanel.Application.Configs.Rotate;
 using PnvPanel.Application.Tests.TestSupport;
+using PnvPanel.Domain.Activation;
+using PnvPanel.Domain.Apps;
+using PnvPanel.Domain.Audit;
+using PnvPanel.Domain.Billing;
 using PnvPanel.Domain.Configs;
 using PnvPanel.Domain.Inbounds;
+using PnvPanel.Domain.Instructions;
+using PnvPanel.Domain.News;
 using PnvPanel.Domain.Nodes;
+using PnvPanel.Domain.Pricing;
+using PnvPanel.Domain.Support;
+using PnvPanel.Domain.Telegram;
+using PnvPanel.Infrastructure.Persistence;
 using Xunit;
 
 namespace PnvPanel.Application.Tests.Configs.Rotate;
 
+/// <summary>Оборачивает реальный AppDbContext, но всегда фейлит SaveChangesAsync — симулирует сбой БД
+/// после успешного создания клиента в панели (DbUpdateException — единственный тип, который ловит
+/// RotateVpnConfigCommandHandler для компенсирующего отката).</summary>
+public sealed class ThrowingSaveDbContext(AppDbContext inner) : IAppDbContext
+{
+    public DbSet<ActivationRequest> ActivationRequests => inner.ActivationRequests;
+    public DbSet<AuditLog> AuditLogs => inner.AuditLogs;
+    public DbSet<TelegramLinkToken> TelegramLinkTokens => inner.TelegramLinkTokens;
+    public DbSet<TelegramLoginRequest> TelegramLoginRequests => inner.TelegramLoginRequests;
+    public DbSet<Node> Nodes => inner.Nodes;
+    public DbSet<Inbound> Inbounds => inner.Inbounds;
+    public DbSet<VpnConfig> VpnConfigs => inner.VpnConfigs;
+    public DbSet<TrafficSample> TrafficSamples => inner.TrafficSamples;
+    public DbSet<ClientApp> ClientApps => inner.ClientApps;
+    public DbSet<NewsPost> NewsPosts => inner.NewsPosts;
+    public DbSet<SupportTicket> SupportTickets => inner.SupportTickets;
+    public DbSet<TicketComment> TicketComments => inner.TicketComments;
+    public DbSet<TicketAttachment> TicketAttachments => inner.TicketAttachments;
+    public DbSet<InstructionIntro> InstructionIntros => inner.InstructionIntros;
+    public DbSet<InstructionTab> InstructionTabs => inner.InstructionTabs;
+    public DbSet<PricingSettings> PricingSettings => inner.PricingSettings;
+    public DbSet<PricingDiscountTier> PricingDiscountTiers => inner.PricingDiscountTiers;
+    public DbSet<BillingSettings> BillingSettings => inner.BillingSettings;
+    public DbSet<PaymentRequest> PaymentRequests => inner.PaymentRequests;
+    public DatabaseFacade Database => inner.Database;
+
+    public Task<int> SaveChangesAsync(CancellationToken cancellationToken) =>
+        throw new DbUpdateException("simulated failure");
+}
+
 public class RotateVpnConfigCommandHandlerTests
 {
     private readonly IXuiPanelGateway _gateway = Substitute.For<IXuiPanelGateway>();
@@ -231,4 +273,76 @@ public class RotateVpnConfigCommandHandlerTests
         Assert.Equal(gatewayError, result.Error);
         Assert.Equal("old-external-id", config.ClientExternalId);
     }
+
+    [Fact]
+    public async Task Handle_WhenSaveChangesFailsAfterAddClient_RemovesOrphanedClientAndReturnsRotateFailed()
+    {
+        using var dbContext = InMemoryDbContextFactory.Create();
+        var userId = Guid.NewGuid();
+        _identityService
+            .GetProfileAsync(userId, Arg.Any<CancellationToken>())
+            .Returns(MakeProfile(userId));
+
+        var node = Node.Register(
+            "node-1",
+            new Uri("https://node1.example.com"),
+            new NodeCredentials("admin", "protected"),
+            null
+        );
+        var inbound = Inbound.FromRemote(node.Id, "1", VpnProtocol.Vless, "remark", 443);
+        var config = VpnConfig.Create(userId, inbound.Id, VpnProtocol.Vless, null);
+        config.AssignRemoteClient("old-external-id");
+
+        dbContext.Nodes.Add(node);
+        dbContext.Inbounds.Add(inbound);
+        dbContext.VpnConfigs.Add(config);
+        await dbContext.SaveChangesAsync(CancellationToken.None);
+
+        _gateway
+            .AddClientAsync(
+                Arg.Any<Node>(),
+                inbound.RemoteInboundId,
+                config.Protocol,
+                Arg.Any<string>(),
+                Arg.Any<string>(),
+                Arg.Any<int>(),
+                Arg.Any<DateTimeOffset?>(),
+                Arg.Any<CancellationToken>()
+            )
+            .Returns(Result.Success("new-external-id"));
+
+        var handler = new RotateVpnConfigCommandHandler(
+            new ThrowingSaveDbContext(dbContext),
+            _gateway,
+            _identityService,
+            FakeCurrentUser.Authenticated(userId)
+        );
+
+        var result = await handler.Handle(
+            new RotateVpnConfigCommand(config.Id),
+            CancellationToken.None
+        );
+
+        Assert.False(result.IsSuccess);
+        Assert.Equal(ConfigErrors.RotateFailed, result.Error);
+        // Осиротевший клиент, успевший создаться в панели до сбоя SaveChanges, откатывается.
+        await _gateway
+            .Received(1)
+            .RemoveClientAsync(
+                Arg.Any<Node>(),
+                inbound.RemoteInboundId,
+                "new-external-id",
+                config.Protocol,
+                Arg.Any<CancellationToken>()
+            );
+        await _gateway
+            .DidNotReceive()
+            .RemoveClientAsync(
+                Arg.Any<Node>(),
+                inbound.RemoteInboundId,
+                "old-external-id",
+                config.Protocol,
+                Arg.Any<CancellationToken>()
+            );
+    }
 }