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.API/Services/MenuService.cs

@@ -139,7 +139,8 @@ public class MenuService : IMenuService
             ImageUrl = imageUrl,
             VideoUrl = request.VideoUrl,
             Model3dUrl = NormalizeOptionalText(request.Model3dUrl),
-            IsAvailable = request.IsAvailable
+            IsAvailable = request.IsAvailable,
+            KitchenStationId = string.IsNullOrWhiteSpace(request.KitchenStationId) ? null : request.KitchenStationId,
         };
 
         _db.MenuItems.Add(entity);
@@ -178,6 +179,8 @@ public class MenuService : IMenuService
         if (request.Model3dUrl is not null)
             entity.Model3dUrl = string.IsNullOrWhiteSpace(request.Model3dUrl) ? null : request.Model3dUrl.Trim();
         if (request.IsAvailable.HasValue) entity.IsAvailable = request.IsAvailable.Value;
+        if (request.KitchenStationId is not null)
+            entity.KitchenStationId = string.IsNullOrWhiteSpace(request.KitchenStationId) ? null : request.KitchenStationId;
 
         await _db.SaveChangesAsync(cancellationToken);
         return ToItemDto(entity);
@@ -236,5 +239,6 @@ public class MenuService : IMenuService
         MenuItemImageDefaults.ResolveDisplayImageUrl(i),
         i.VideoUrl,
         i.Model3dUrl,
-        i.IsAvailable);
+        i.IsAvailable,
+        i.KitchenStationId);
 }