feat(api): .NET 10 multi-tenant REST API

Full backend implementation:
- Multi-tenant cafe/restaurant management (menus, orders, tables, staff)
- POS order flow with ZarinPal and Snappfood payment integration
- OTP authentication via Kavenegar SMS
- QR digital menu with public discover/finder endpoints
- Customer loyalty, coupons, CRM
- PostgreSQL via EF Core, Redis for caching/sessions
- Background jobs, webhook handlers
- Full migration history

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/Meezi.API/Services/KdsNotifier.cs

@@ -0,0 +1,25 @@
+using Microsoft.AspNetCore.SignalR;
+using Meezi.API.Hubs;
+using Meezi.API.Models.Orders;
+using Meezi.Core.Enums;
+
+namespace Meezi.API.Services;
+
+public class KdsNotifier : IKdsNotifier
+{
+    private readonly IHubContext<KdsHub> _hubContext;
+
+    public KdsNotifier(IHubContext<KdsHub> hubContext)
+    {
+        _hubContext = hubContext;
+    }
+
+    public Task NotifyOrderCreatedAsync(string cafeId, LiveOrderDto order, CancellationToken cancellationToken = default) =>
+        _hubContext.Clients.Group(KdsHub.GroupName(cafeId)).SendAsync("OrderCreated", order, cancellationToken);
+
+    public Task NotifyOrderStatusChangedAsync(string cafeId, string orderId, OrderStatus status, CancellationToken cancellationToken = default) =>
+        _hubContext.Clients.Group(KdsHub.GroupName(cafeId)).SendAsync("OrderStatusChanged", new { orderId, status }, cancellationToken);
+
+    public Task NotifyTableStatusChangedAsync(string cafeId, CancellationToken cancellationToken = default) =>
+        _hubContext.Clients.Group(KdsHub.GroupName(cafeId)).SendAsync("TableStatusChanged", null, cancellationToken);
+}