feat: ESP32 DIY platform Phase 1 — marketplace with mock payment & flash token flow

- React+Vite frontend (dark theme, role-based routing: admin/seller/buyer)
- Express+Prisma+PostgreSQL backend with JWT auth and audit logging
- MinIO object storage with backend proxy for CORS-free firmware delivery
- Mock payment flow (order → mock-pay → FlashToken) for pre-business testing
- FlashToken lifecycle: issue → validate → esp-web-tools manifest → consume
- Admin approval workflow for project/product submissions
- Toss Payments integration guide (TOSS_PAYMENT_GUIDE.md) for live keys

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

backend/src/config/redis.js

@@ -0,0 +1,10 @@
+const Redis = require('ioredis');
+
+const redis = new Redis(process.env.REDIS_URL || 'redis://localhost:6379', {
+  maxRetriesPerRequest: 3,
+  lazyConnect: true,
+});
+
+redis.on('error', (err) => console.error('Redis error:', err.message));
+
+module.exports = redis;