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/WizardProvider.tsx

@@ -31,7 +31,10 @@ interface WizardActions {
 
 // Only the actions are shared — the open flag stays local to the provider (it renders the wizard
 // itself), so no consumer needs to subscribe to it.
-const ActionsContext = createContext<WizardActions>({ openWizard: () => {}, closeWizard: () => {} });
+const ActionsContext = createContext<WizardActions>({
+  openWizard: () => {},
+  closeWizard: () => {},
+});
 
 export function useWizard(): WizardActions {
   return useContext(ActionsContext);
@@ -51,7 +54,10 @@ export function WizardProvider({ children }: { children: ReactNode }) {
     if (me && shouldAutoOpenOnboarding(me)) setOpen(true);
   }, [me?.id, me?.can_read, me?.can_write]);
 
-  const actions = useMemo<WizardActions>(() => ({ openWizard, closeWizard }), [openWizard, closeWizard]);
+  const actions = useMemo<WizardActions>(
+    () => ({ openWizard, closeWizard }),
+    [openWizard, closeWizard],
+  );
 
   return (
     <ActionsContext.Provider value={actions}>