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/Printing/NetworkPrinterService.cs

@@ -76,15 +76,16 @@ public class NetworkPrinterService : IPrinterService
             return PrintResult.Ok();
 
         var menuItemIds = activeItems.Select(i => i.MenuItemId).Distinct().ToList();
-        var categoryStations = await (
+        // Per-item station overrides the category's station; fall back to category.
+        var itemStations = await (
             from m in _db.MenuItems.AsNoTracking()
             join c in _db.MenuCategories.AsNoTracking() on m.CategoryId equals c.Id
             where menuItemIds.Contains(m.Id) && m.CafeId == cafeId
-            select new { m.Id, c.KitchenStationId }
+            select new { m.Id, StationId = m.KitchenStationId ?? c.KitchenStationId }
         ).ToListAsync(ct);
 
-        var stationIds = categoryStations
-            .Select(x => x.KitchenStationId)
+        var stationIds = itemStations
+            .Select(x => x.StationId)
             .Where(id => !string.IsNullOrEmpty(id))
             .Distinct()
             .ToList();
@@ -99,8 +100,8 @@ public class NetworkPrinterService : IPrinterService
         var groups = activeItems
             .GroupBy(item =>
             {
-                var cat = categoryStations.FirstOrDefault(c => c.Id == item.MenuItemId);
-                return cat?.KitchenStationId;
+                var map = itemStations.FirstOrDefault(c => c.Id == item.MenuItemId);
+                return map?.StationId;
             })
             .ToList();