feat(worker): add logout + replace admin-only settings with Account screen

The Instellingen tab was activity management, which Phase 2 made admin-only —
workers saw add/edit/delete controls that all 403. Replace it with an Account
tab showing the signed-in name/email (via /api/me) and an Uitloggen button
(wires the existing AuthContext signOut). Activity management belongs to the
Phase 3 admin app, so the worker client drops the Settings screen and its
now-unused activity-mutation hooks (useActivities read stays).

Products affected: SoleLog worker client (apps/worker).

apps/worker/src/components/TabBar.tsx

@@ -3,7 +3,7 @@ import { NavLink } from 'react-router-dom';
 const tabs = [
   { to: '/', label: 'Stopwatch' },
   { to: '/history', label: 'Geschiedenis' },
-  { to: '/settings', label: 'Instellingen' },
+  { to: '/account', label: 'Account' },
 ] as const;
 
 export default function TabBar() {