fix: skip retries on 404 for single-resource queries

Prevents 10-second loading skeleton when navigating to non-existent
threads, setups, or items. Shows error/not-found state immediately.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/hooks/useItems.ts

@@ -1,6 +1,13 @@
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import type { CreateItem } from "../../shared/types";
-import { apiDelete, apiGet, apiPost, apiPut, apiUpload } from "../lib/api";
+import {
+	ApiError,
+	apiDelete,
+	apiGet,
+	apiPost,
+	apiPut,
+	apiUpload,
+} from "../lib/api";
 
 interface Item {
 	id: number;
@@ -45,6 +52,8 @@ export function useItem(id: number | null) {
 		queryKey: ["items", id],
 		queryFn: () => apiGet<ItemWithCategory>(`/api/items/${id}`),
 		enabled: id != null,
+		retry: (count, error) =>
+			error instanceof ApiError && error.status === 404 ? false : count < 3,
 	});
 }