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/src/components/menu/menu-admin-screen.tsx

@@ -12,8 +12,9 @@ import { CategoryVisual } from "@/components/menu/category-visual";
 import { CategoryMediaFields } from "@/components/menu/category-media-fields";
 import type { CategoryIconSelection } from "@/components/menu/category-preset-picker";
 import { DEFAULT_CATEGORY_ICON_STYLE } from "@/lib/category-icon-presets";
-import { ApiClientError, apiGet, apiPatch, apiPost } from "@/lib/api/client";
+import { apiGet, apiPatch, apiPost } from "@/lib/api/client";
 import { notify } from "@/lib/notify";
+import { useApiError } from "@/lib/use-api-error";
 import { useAuthStore } from "@/lib/stores/auth.store";
 import { useBranchStore } from "@/lib/stores/branch.store";
 import { formatCurrency, formatNumber } from "@/lib/format";
@@ -184,11 +185,8 @@ function Modal({
 export function MenuAdminScreen() {
   const t = useTranslations("menuAdmin");
   const tCommon = useTranslations("common");
-  const tNotify = useTranslations("notify");
-  const showError = (err: unknown) =>
-    notify.error(
-      err instanceof ApiClientError ? err.message : tNotify("errorGeneric")
-    );
+  const apiError = useApiError();
+  const showError = (err: unknown) => notify.error(apiError(err));
   const isRtl = useIsRtl();
   const locale = useLocale();
   const numberLocale = locale === "en" ? "en-US" : "fa-IR";