fix(i18n): localize API error messages by code (no more raw English)

Error toasts surfaced the raw English backend message. Added an errors namespace (fa/ar/en) keyed by error code + a useApiError() resolver that maps ApiClientError.code to the localized message (fallback to a localized generic). Wired into menu, tables, demo banner, and subscription checkout; hardened getErrorMessage so it never returns the raw backend message.

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

web/dashboard/messages/en.json

@@ -20,6 +20,33 @@
     "saved": "Saved",
     "errorGeneric": "Something went wrong. Please try again."
   },
+  "errors": {
+    "generic": "Something went wrong. Please try again.",
+    "REQUEST_FAILED": "Request failed. Please try again.",
+    "VALIDATION_ERROR": "The information entered is invalid.",
+    "FORBIDDEN": "You don't have permission to do this.",
+    "OWNER_REQUIRED": "Only the café owner can do this.",
+    "MANAGER_REQUIRED": "This action requires manager access.",
+    "PLAN_LIMIT_REACHED": "You've reached your plan limit. Upgrade to continue.",
+    "PLAN_FEATURE_DISABLED": "This feature isn't available on your current plan.",
+    "NOT_FOUND": "Not found.",
+    "ORDER_NOT_FOUND": "Order not found.",
+    "ITEM_NOT_FOUND": "Item not found.",
+    "ITEM_ALREADY_VOIDED": "This item is already voided.",
+    "ORDER_ALREADY_CLOSED": "This order is already closed.",
+    "TABLE_OCCUPIED": "This table is currently occupied.",
+    "TABLE_CLEANING": "This table is being cleaned.",
+    "TABLE_NOT_FOUND": "Table not found.",
+    "TABLE_HAS_OPEN_ORDER": "This table has an open order and can't be removed.",
+    "TABLE_SECTION_HAS_TABLES": "This section has tables and can't be removed.",
+    "BRANCH_NOT_FOUND": "Branch not found.",
+    "SECTION_NOT_FOUND": "Section not found.",
+    "RATE_LIMITED": "Too many requests. Please wait a moment.",
+    "SMS_FAILED": "Could not send the SMS. Please try again.",
+    "INVALID_OTP": "Invalid or expired verification code.",
+    "TICKET_CLOSED": "This ticket is closed and can't receive messages.",
+    "ALREADY_REGISTERED": "An account already exists for this number. Please sign in."
+  },
   "brand": {
     "name": "Meezi"
   },