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/studio/layout.tsx

@@ -0,0 +1,77 @@
+"use client";
+
+import {
+	BadgeCheck,
+	Cat,
+	ClipboardCheck,
+	Copy,
+	Dumbbell,
+	Image as ImageIcon,
+	type LucideIcon,
+	Puzzle,
+	RefreshCw,
+	Shirt,
+	Upload,
+	Wrench,
+} from "lucide-react";
+import Link from "next/link";
+import { usePathname } from "next/navigation";
+import { cn } from "@/lib/utils";
+
+const TABS: { href: string; label: string; icon: LucideIcon }[] = [
+	{ href: "/admin/studio/furni", label: "Furni", icon: Puzzle },
+	{ href: "/admin/studio/upload", label: "Upload", icon: Upload },
+	{ href: "/admin/studio/badges", label: "Badges", icon: BadgeCheck },
+	{ href: "/admin/studio/clothing", label: "Clothing", icon: Shirt },
+	{ href: "/admin/studio/effects", label: "Effects", icon: Dumbbell },
+	{ href: "/admin/studio/pets", label: "Pets", icon: Cat },
+	{ href: "/admin/studio/clone", label: "Clone", icon: Copy },
+	{ href: "/admin/studio/sync", label: "Sync", icon: RefreshCw },
+	{
+		href: "/admin/studio/repair-icons",
+		label: "Repair Icons",
+		icon: ImageIcon,
+	},
+	{ href: "/admin/studio/audit", label: "Audit", icon: ClipboardCheck },
+	{
+		href: "/admin/studio/maintenance",
+		label: "Catalogus onderhoud",
+		icon: Wrench,
+	},
+];
+
+export default function StudioLayout({
+	children,
+}: {
+	children: React.ReactNode;
+}) {
+	const pathname = usePathname() ?? "";
+	return (
+		<div
+			className="flex h-[calc(100dvh-7rem)] min-h-[520px] flex-col overflow-hidden rounded-xl border border-[var(--admin-border)]"
+			style={{ backgroundColor: "var(--admin-canvas)" }}
+		>
+			<div className="flex shrink-0 items-center gap-1 overflow-x-auto border-b border-[var(--admin-border)] bg-[var(--admin-surface)] px-2 py-1.5">
+				{TABS.map(({ href, label, icon: Icon }) => {
+					const active = pathname === href || pathname.startsWith(`${href}/`);
+					return (
+						<Link
+							key={href}
+							href={href}
+							className={cn(
+								"flex shrink-0 items-center gap-1.5 rounded-md px-2.5 py-1.5 text-xs font-medium transition-colors",
+								active
+									? "bg-[var(--admin-accent)] text-[var(--admin-accent-foreground)]"
+									: "text-[var(--admin-text-muted)] hover:bg-[var(--admin-accent)]/10 hover:text-[var(--admin-text)]",
+							)}
+						>
+							<Icon size={13} />
+							{label}
+						</Link>
+					);
+				})}
+			</div>
+			<div className="min-h-0 flex-1 overflow-auto">{children}</div>
+		</div>
+	);
+}