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/backend/Dockerfile

@@ -0,0 +1,19 @@
+FROM node:20-alpine
+
+# ffmpeg (영상 압축, 2단계에서 사용)
+RUN apk add --no-cache ffmpeg
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci --omit=dev
+
+COPY prisma ./prisma
+RUN npx prisma generate
+
+COPY src ./src
+
+EXPOSE 3201
+
+# 마이그레이션 후 서버 시작
+CMD ["sh", "-c", "npx prisma migrate deploy && node src/index.js"]