fix(studio): harden organize-imports against long-running queries and hangs

The original GET route used a correlated NOT EXISTS / FIND_IN_SET
subquery over the entire catalog_items table for every recent import
audit entry, causing server timeouts when the audit log or catalog
grew large.  The per-item host-page validation inside the create
action also issued one SELECT + one UPDATE per moved offer.

Changes:
- GET /api/admin/import/organize: replace the correlated subquery
  with a bounded candidate list and a JS-side placed-set check, then
  resolve all needed base items in a single indexed SELECT.  This
  bounds the query cost regardless of catalog or audit log size.
- organizeImportFurni action: validate mover ids in one SELECT, then
  batch every move per group into a single UPDATE with a CASE
  expression instead of one UPDATE per item.
- OrganizeImportsDialog: add a 45-second abort timeout on the fetch
  and a distinct load-error state so the UI never silently hangs.
- Add 'loadError' translation key (en + nl).

src/components/admin/studio/organize-imports-dialog.tsx

@@ -75,6 +75,7 @@ export function OrganizeImportsDialog({
 	const router = useRouter();
 
 	const [loading, setLoading] = useState(false);
+	const [loadError, setLoadError] = useState(false);
 	const [items, setItems] = useState<OrganizeItem[]>([]);
 	const [rootPages, setRootPages] = useState<RootPage[]>([]);
 	const [importRootPageId, setImportRootPageId] = useState<number | null>(null);
@@ -96,10 +97,17 @@ export function OrganizeImportsDialog({
 
 	const load = useCallback(async () => {
 		setLoading(true);
+		setLoadError(false);
+		const controller = new AbortController();
+		const timeout = setTimeout(() => controller.abort(), 45000);
 		try {
 			const [data, tree] = await Promise.all([
-				fetch("/api/admin/import/organize").then((r) => r.json()),
-				fetch("/api/admin/catalog/tree?parentId=-1").then((r) => r.json()),
+				fetch("/api/admin/import/organize", { signal: controller.signal }).then(
+					(r) => r.json(),
+				),
+				fetch("/api/admin/catalog/tree?parentId=-1", {
+					signal: controller.signal,
+				}).then((r) => r.json()),
 			]);
 			setItems(Array.isArray(data?.items) ? data.items : []);
 			setImportRootPageId(data?.importRootPageId ?? null);
@@ -113,8 +121,10 @@ export function OrganizeImportsDialog({
 			);
 		} catch (error) {
 			console.error("[OrganizeImports] load failed:", error);
-			toast.error("Failed to load imports");
+			setLoadError(true);
+			setItems([]);
 		} finally {
+			clearTimeout(timeout);
 			setLoading(false);
 		}
 	}, []);
@@ -347,7 +357,7 @@ export function OrganizeImportsDialog({
 						</div>
 					) : items.length === 0 ? (
 						<div className="flex flex-1 flex-col items-center justify-center gap-3 text-sm text-muted-foreground">
-							{t("empty")}
+							{loadError ? t("loadError") : t("empty")}
 							<Button
 								type="button"
 								variant="outline"