feat(menu): per-item print station (cold bar / kitchen / barista)

Each menu item can now pick its own print station, overriding the category's —
so a category can fan out to different printers (e.g. a drink → cold bar, a
food → kitchen). Adds MenuItem.KitchenStationId (+ migration, FK SetNull), wires
create/update/DTO, and updates kitchen-ticket routing to group by the item's
station ?? the category's station ?? the branch kitchen printer. Deleting a
station now also clears item assignments. Menu item editor gains a "Print
station" dropdown (default = "same as category"). fa/en/ar added.

Backend built clean via the Nexus mirror; migration applies on deploy (MigrateAsync).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Meezi.Core/Entities/KitchenStation.cs

@@ -12,4 +12,5 @@ public class KitchenStation : TenantEntity
     public Cafe Cafe { get; set; } = null!;
     public Branch? Branch { get; set; }
     public ICollection<MenuCategory> Categories { get; set; } = [];
+    public ICollection<MenuItem> MenuItems { get; set; } = [];
 }

src/Meezi.Core/Entities/MenuItem.cs

@@ -15,9 +15,13 @@ public class MenuItem : TenantEntity
     /// <summary>GLB/GLTF 3D model for QR menu interactive view (poster = ImageUrl).</summary>
     public string? Model3dUrl { get; set; }
     public bool IsAvailable { get; set; } = true;
+    /// <summary>Optional per-item print station (cold bar, kitchen, barista …).
+    /// Overrides the item's category station when set.</summary>
+    public string? KitchenStationId { get; set; }
 
     public Cafe Cafe { get; set; } = null!;
     public MenuCategory Category { get; set; } = null!;
+    public KitchenStation? KitchenStation { get; set; }
     public ICollection<OrderItem> OrderItems { get; set; } = [];
     public ICollection<BranchMenuItemOverride> BranchOverrides { get; set; } = [];
     public ICollection<MenuItemIngredient> RecipeIngredients { get; set; } = [];