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/api/activities.ts

@@ -1,51 +1,12 @@
-import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
-import type { Activity, CreateActivityInput, UpdateActivityInput } from '@solelog/shared';
+import { useQuery } from '@tanstack/react-query';
+import type { Activity } from '@solelog/shared';
 import { apiFetch } from '../lib/api';
 
+// Activities are read-only in the worker client; managing them is admin-only
+// and lives in the Phase 3 admin app.
 export function useActivities() {
   return useQuery({
     queryKey: ['activities'],
     queryFn: () => apiFetch<Activity[]>('/api/activities'),
   });
 }
-
-export function useCreateActivity() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (input: CreateActivityInput) =>
-      apiFetch<Activity>('/api/activities', {
-        method: 'POST',
-        body: JSON.stringify(input),
-      }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['activities'] });
-    },
-  });
-}
-
-export function useUpdateActivity() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, input }: { id: number; input: UpdateActivityInput }) =>
-      apiFetch<Activity>(`/api/activities/${id}`, {
-        method: 'PUT',
-        body: JSON.stringify(input),
-      }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['activities'] });
-    },
-  });
-}
-
-export function useDeleteActivity() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: number) =>
-      apiFetch<{ success: true }>(`/api/activities/${id}`, { method: 'DELETE' }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['activities'] });
-      // Deleting an activity cascades to its work sessions on the server.
-      queryClient.invalidateQueries({ queryKey: ['sessions'] });
-    },
-  });
-}

apps/worker/src/api/me.ts

@@ -0,0 +1,11 @@
+import { useQuery } from '@tanstack/react-query';
+import type { MeResponse } from '@solelog/shared';
+import { apiFetch } from '../lib/api';
+
+// The signed-in user (id, email, name). Used by the Account screen.
+export function useMe() {
+  return useQuery({
+    queryKey: ['me'],
+    queryFn: () => apiFetch<MeResponse>('/api/me'),
+  });
+}