Refactor to enforce AuthContext usage over useAuthStore and improve test stability

- Replaced `useAuthStore` with `useAuth` from `AuthContext` across frontend components and tests to ensure dependency injection compliance.
- Enhanced E2E test stability by delaying navigation until the auth context is fully initialized.
- Updated Playwright configuration to use a single worker to prevent mock conflicts.
- Refactored test setup to consistently inject `AuthProvider` for improved isolation and mocking.
- Adjusted comments and documentation to clarify dependency injection and testability patterns.

frontend/src/lib/api/hooks/useUser.ts

@@ -9,7 +9,7 @@
 
 import { useMutation, useQueryClient } from '@tanstack/react-query';
 import { updateCurrentUser } from '../client';
-import { useAuthStore } from '@/lib/stores/authStore';
+import { useAuth } from '@/lib/auth/AuthContext';
 import type { User } from '@/lib/stores/authStore';
 import { parseAPIError, getGeneralError } from '../errors';
 import { authKeys } from './useAuth';
@@ -31,7 +31,7 @@ import { authKeys } from './useAuth';
  */
 export function useUpdateProfile(onSuccess?: (message: string) => void) {
   const queryClient = useQueryClient();
-  const setUser = useAuthStore((state) => state.setUser);
+  const setUser = useAuth((state) => state.setUser);
 
   return useMutation({
     mutationFn: async (data: {