feat: Add login/logout audit logging (refs #10)

Backend:
- Add login event logging to getUserStatus() controller method
- Create POST /auth/track-logout endpoint for logout tracking

Frontend:
- Create useLogout hook that wraps Auth0 logout with audit tracking
- Update all logout locations to use the new hook (SettingsPage,
  Layout, MobileSettingsScreen, useDeletion)

Login events are logged when the frontend calls /auth/user-status after
Auth0 callback. Logout events are logged via fire-and-forget call to
/auth/track-logout before Auth0 logout.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/features/settings/hooks/useDeletion.ts

@@ -4,6 +4,7 @@
 
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useAuth0 } from '@auth0/auth0-react';
+import { useLogout } from '../../../core/auth/useLogout';
 import { profileApi } from '../api/profile.api';
 import { RequestDeletionRequest } from '../types/profile.types';
 import toast from 'react-hot-toast';
@@ -36,7 +37,7 @@ export const useDeletionStatus = () => {
 
 export const useRequestDeletion = () => {
   const queryClient = useQueryClient();
-  const { logout } = useAuth0();
+  const { logout } = useLogout();
 
   return useMutation({
     mutationFn: (data: RequestDeletionRequest) => profileApi.requestDeletion(data),
@@ -45,9 +46,9 @@ export const useRequestDeletion = () => {
       queryClient.invalidateQueries({ queryKey: ['user-profile'] });
       toast.success(response.data.message || 'Account deletion scheduled');
 
-      // Logout after 2 seconds
+      // Logout after 2 seconds (with audit tracking)
       setTimeout(() => {
-        logout({ logoutParams: { returnTo: window.location.origin } });
+        logout();
       }, 2000);
     },
     onError: (error: ApiError) => {