fix: Import useEffect to fix React is not defined error

Added missing useEffect import in AppShell.tsx. The debug logging code
was using useEffect but it wasn't imported, causing the app to crash.

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

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

maternal-web/components/layouts/AppShell/AppShell.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useState } from 'react';
+import { useState, useEffect } from 'react';
 import {
   Box,
   Container,
@@ -38,7 +38,7 @@ export const AppShell = ({ children }: AppShellProps) => {
   const [anchorEl, setAnchorEl] = useState<null | HTMLElement>(null);
 
   // Debug: Log user photo changes
-  React.useEffect(() => {
+  useEffect(() => {
     console.log('👤 User updated in AppShell:', {
       name: user?.name,
       hasPhoto: !!user?.photoUrl,