fix: remove default sort=-updated from listOne to prevent PocketBase 400 errors

Collections without an 'updated' field (books, user_sessions, user_settings,
user_library) were returning 400 because listOne always sent sort=-updated.
Changed default to empty string since we only fetch 1 record (no ordering needed).

ui/src/lib/server/pocketbase.ts

@@ -197,8 +197,9 @@ async function countCollection(collection: string, filter = ''): Promise<number>
 	return (data as { totalItems: number }).totalItems ?? 0;
 }
 
-async function listOne<T>(collection: string, filter: string, sort = '-updated'): Promise<T | null> {
-	const params = new URLSearchParams({ perPage: '1', filter, sort });
+async function listOne<T>(collection: string, filter: string, sort = ''): Promise<T | null> {
+	const params = new URLSearchParams({ perPage: '1', filter });
+	if (sort) params.set('sort', sort);
 	const data = await pbGet<PBList<T>>(
 		`/api/collections/${collection}/records?${params.toString()}`
 	);