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.Core/Entities/BranchMenuItemOverride.cs

@@ -0,0 +1,18 @@
+namespace Meezi.Core.Entities;
+
+/// <summary>Per-branch availability and price override for a catalog menu item.</summary>
+public class BranchMenuItemOverride : TenantEntity
+{
+    public string BranchId { get; set; } = string.Empty;
+    public string MenuItemId { get; set; } = string.Empty;
+    /// <summary>false = hidden at this branch.</summary>
+    public bool IsAvailable { get; set; } = true;
+    /// <summary>null = use MenuItem.Price.</summary>
+    public decimal? PriceOverride { get; set; }
+    public int? SortOrderOverride { get; set; }
+    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
+    public string? UpdatedByUserId { get; set; }
+
+    public Branch Branch { get; set; } = null!;
+    public MenuItem MenuItem { get; set; } = null!;
+}