feat: add ESP32 DIY platform Phase 1 (marketplace scaffold)

- Docker Compose with Postgres, Redis, MinIO, backend, frontend (port 3200/3201)
- Prisma schema: User, Project, ProjectFile, Product, Order, FlashToken, Review, AuditLog
- Backend: JWT auth, project CRUD + file upload (MinIO + sharp WebP), admin approval flow
- Frontend: React + Vite SPA with auth, project/shop browse, seller dashboard, admin panel
- Admin: pending approval queue, user management, audit log viewer, stats dashboard
- Audit logging middleware for legal compliance
- Admin init script: createAdmin.js
- Full design document in PLATFORM_DESIGN.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

platform/frontend/src/hooks/useAuth.js

@@ -0,0 +1,53 @@
+import { createContext, useContext, useState, useEffect } from 'react';
+import api from '../api/client';
+
+const AuthContext = createContext(null);
+
+export function AuthProvider({ children }) {
+  const [user, setUser]       = useState(() => {
+    try { return JSON.parse(localStorage.getItem('user')); } catch { return null; }
+  });
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    const token = localStorage.getItem('token');
+    if (!token) { setLoading(false); return; }
+    api.get('/auth/me')
+      .then(r => { setUser(r.data); localStorage.setItem('user', JSON.stringify(r.data)); })
+      .catch(() => { localStorage.removeItem('token'); localStorage.removeItem('user'); setUser(null); })
+      .finally(() => setLoading(false));
+  }, []);
+
+  async function login(email, password) {
+    const { data } = await api.post('/auth/login', { email, password });
+    localStorage.setItem('token', data.token);
+    localStorage.setItem('user', JSON.stringify(data.user));
+    setUser(data.user);
+    return data.user;
+  }
+
+  async function register(email, password, nickname) {
+    const { data } = await api.post('/auth/register', { email, password, nickname });
+    localStorage.setItem('token', data.token);
+    localStorage.setItem('user', JSON.stringify(data.user));
+    setUser(data.user);
+    return data.user;
+  }
+
+  async function logout() {
+    try { await api.post('/auth/logout'); } catch {}
+    localStorage.removeItem('token');
+    localStorage.removeItem('user');
+    setUser(null);
+  }
+
+  return (
+    <AuthContext.Provider value={{ user, loading, login, register, logout }}>
+      {children}
+    </AuthContext.Provider>
+  );
+}
+
+export function useAuth() {
+  return useContext(AuthContext);
+}