feat: relocate import tools into studio and harden catalog/furnidata integrity

- Move /admin/import/* tools under /admin/studio/* and add studio nav, layout and tabs
- Add shared catalog maintenance panel plus a /admin/studio/maintenance tab
- Make furnidata reconciliation overwrite conflicting entries with the
  DB-authoritative items_base classname/id (surfaced via fixedConflicts)
- Add furnidata_translate_enabled setting to skip the heavy localized
  furnidata build during import (manual build-languages still forces it)
- Update staff smoke contract test for the studio hub

src/app/admin/import/effects/loading.tsx

@@ -1,17 +0,0 @@
-// src/app/[locale]/admin/import/effects/loading.tsx
-export default function Loading() {
-	return (
-		<div className="grid grid-cols-2 md:grid-cols-4 lg:grid-cols-6 gap-3">
-			{Array.from({ length: 18 }, (_, i) => i).map((n) => (
-				<div
-					key={`effect-skeleton-${n}`}
-					className="rounded-lg border bg-card p-3 animate-pulse"
-				>
-					<div className="h-12 w-12 bg-muted rounded mx-auto mb-2" />
-					<div className="h-4 bg-muted rounded w-3/4 mx-auto mb-1" />
-					<div className="h-7 bg-muted rounded" />
-				</div>
-			))}
-		</div>
-	);
-}

src/app/admin/import/effects/page.tsx

@@ -1,14 +0,0 @@
-// src/app/[locale]/admin/import/effects/page.tsx
-import { redirect } from "next/navigation";
-import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
-import { ImportEffectsClient } from "./import-effects-client";
-
-export default async function ImportEffectsPage(_props: {
-	params: Promise<{ locale: string }>;
-}) {
-	const { session, permissions } = await getAdminContext();
-	if (!canAccess(permissions, PERMS.ASSETS_IMPORT, session.user.rank)) {
-		redirect("/admin");
-	}
-	return <ImportEffectsClient />;
-}