fix(bot): register DirectSessionNotificationSender in DI

src/GmRelay.Bot/Program.cs

@@ -79,6 +79,8 @@ builder.Services.AddSingleton<HandleRescheduleTimeInputHandler>();
 builder.Services.AddSingleton<HandleRescheduleVoteHandler>();
 builder.Services.AddSingleton<RescheduleVotingFinalizer>();
 
+builder.Services.AddSingleton<DirectSessionNotificationSender>();
+
 // ── Telegram infrastructure ──────────────────────────────────────────
 builder.Services.AddSingleton<UpdateRouter>();
 builder.Services.AddSingleton<ITelegramUpdateHandler>(sp => sp.GetRequiredService<UpdateRouter>());