feat(payment): add per-user in-memory lock for gateway operations

Introduce IUserPaymentLock to serialize payment initiate and verify flows
per user, preventing concurrent duplicate gateway requests across services.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/CMSMicroservice.Infrastructure/ConfigureServices.cs

@@ -39,6 +39,7 @@ public static class ConfigureServices
         services.AddScoped<IAlertService, AlertService>();
         services.AddScoped<IUserNotificationService, UserNotificationService>();
         services.AddScoped<IKavenegarService, KavenegarService>();
+        services.AddSingleton<IUserPaymentLock, UserPaymentLockService>();
         // Local file manager — files are saved to wwwroot/uploads/ on CMS disk
         services.AddSingleton<CMSMicroservice.Application.Common.FileManager.IFileManager, LocalFileManager>();
         services.AddScoped<IPermissionService, PermissionService>();