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/Dockerfile

@@ -0,0 +1,16 @@
+FROM node:20-alpine
+
+RUN apk add --no-cache ffmpeg openssl
+
+WORKDIR /app
+
+COPY package*.json ./
+COPY prisma ./prisma
+
+RUN npm install --omit=dev
+
+COPY src ./src
+
+EXPOSE 3201
+
+CMD ["sh", "-c", "npx prisma db push --accept-data-loss && node src/index.js"]