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/Models/Menu/MenuDtos.cs

@@ -55,7 +55,8 @@ public record MenuItemDto(
     string? ImageUrl,
     string? VideoUrl,
     string? Model3dUrl,
-    bool IsAvailable);
+    bool IsAvailable,
+    string? KitchenStationId);
 
 public record CreateMenuItemRequest(
     string CategoryId,
@@ -68,7 +69,8 @@ public record CreateMenuItemRequest(
     string? ImageUrl = null,
     string? VideoUrl = null,
     string? Model3dUrl = null,
-    bool IsAvailable = true);
+    bool IsAvailable = true,
+    string? KitchenStationId = null);
 
 public record UpdateMenuItemRequest(
     string? CategoryId,
@@ -81,6 +83,7 @@ public record UpdateMenuItemRequest(
     string? ImageUrl,
     string? VideoUrl,
     string? Model3dUrl,
-    bool? IsAvailable);
+    bool? IsAvailable,
+    string? KitchenStationId);
 
 public record UpdateMenuItemAvailabilityRequest(bool IsAvailable);