web: migrate eslint to flat config, replacing removed next lint

web/src/components/layout/Header.tsx

@@ -36,6 +36,7 @@ export const Header = () => {
 
   // hide menu on path change
   useEffect(() => {
+    // eslint-disable-next-line react-hooks/set-state-in-effect -- intentional: close the menu when navigation changes the path
     setShowMenu(false);
   }, [pathname]);
 

web/src/components/search/SearchShell.tsx

@@ -24,6 +24,7 @@ export function SearchShell({
   const [inputValue, setInputValue] = useState(initialQuery);
   const [isPending, startTransition] = useTransition();
   const lastPushedRef = useRef(initialQuery);
+  // eslint-disable-next-line react-hooks/refs -- deliberate: compares against the last debounced push; a stale read only briefly extends the spinner
   const fetching = isPending || inputValue !== lastPushedRef.current;
 
   const pushQuery = useDebouncedCallback((next: string) => {