style(frontend): Prettier config + one-time repo-wide format pass

Prettier 3 (pinned), printWidth 100, double quotes — chosen to match the existing
hand-formatting and minimise reflow. This commit is ONLY the mechanical format pass
(`prettier --write`) plus the config/ignore/scripts, isolated so it never pollutes a
feature diff. Verified behaviour-neutral: typecheck, eslint (0 errors), and vitest
all green before and after. See .git-blame-ignore-revs — `git blame` skips this sha.

frontend/src/components/FeedViewProvider.tsx

@@ -36,7 +36,9 @@ export function useFeedViewActions(): FeedViewActions {
 }
 
 export function FeedViewProvider({ children }: { children: ReactNode }) {
-  const [view, setViewState] = useState<FeedView>(() => parseFeedView(readAccount(LS.feedView, null)));
+  const [view, setViewState] = useState<FeedView>(() =>
+    parseFeedView(readAccount(LS.feedView, null)),
+  );
   // Passive observer of the account App fetches (enabled:false → reads cache, re-renders on update).
   const { data: me } = useQuery({ queryKey: ["me"], queryFn: api.me, enabled: false });