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>

web/dashboard/messages/ar.json

@@ -917,7 +917,8 @@
     "deleteItemSuccess": "تم حذف الصنف",
     "deleteCategoryConfirmTitle": "حذف الفئة",
     "deleteCategoryConfirmDesc": "هل أنت متأكد من حذف الفئة «{name}»؟",
-    "deleteCategorySuccess": "تم حذف الفئة"
+    "deleteCategorySuccess": "تم حذف الفئة",
+    "printStationInherit": "نفس الفئة"
   },
   "branchMenu": {
     "title": "قائمة الفرع",

web/dashboard/messages/en.json

@@ -951,7 +951,8 @@
     "deleteItemSuccess": "Item deleted",
     "deleteCategoryConfirmTitle": "Delete category",
     "deleteCategoryConfirmDesc": "Are you sure you want to delete the “{name}” category?",
-    "deleteCategorySuccess": "Category deleted"
+    "deleteCategorySuccess": "Category deleted",
+    "printStationInherit": "Same as category"
   },
   "branchMenu": {
     "title": "Branch Menu",

web/dashboard/messages/fa.json

@@ -951,7 +951,8 @@
     "deleteItemSuccess": "آیتم حذف شد",
     "deleteCategoryConfirmTitle": "حذف دسته‌بندی",
     "deleteCategoryConfirmDesc": "آیا از حذف دسته «{name}» مطمئن هستید؟",
-    "deleteCategorySuccess": "دسته حذف شد"
+    "deleteCategorySuccess": "دسته حذف شد",
+    "printStationInherit": "مثل دستهٔ منو"
   },
   "branchMenu": {
     "title": "منوی شعبه",