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/lib/useLiveQuery.ts

@@ -12,7 +12,7 @@ export function useLiveQuery<T>(
   // (e.g. poll faster while a job is running). react-query re-evaluates it after each fetch
   // against fresh data — the right place for this, vs. a React state toggle that can lag or
   // stall the live updates.
-  opts: { intervalMs?: number | ((data: T | undefined) => number); enabled?: boolean } = {}
+  opts: { intervalMs?: number | ((data: T | undefined) => number); enabled?: boolean } = {},
 ) {
   const { intervalMs = 4000, enabled = true } = opts;
   return useQuery({