feat(deploy): 添加 docker-compose 一键部署配置

定义 backend 和 frontend 两个服务：
- backend 监听 3001 端口，设置 Prisma OpenSSL 3.x 环境变量，
  JWT_SECRET 通过宿主机环境变量注入避免硬编码
- frontend 监听 8080 端口，depends_on backend 保证启动顺序

使用方式：
  JWT_SECRET=your-secret docker-compose up -d

docker-compose.yml

@@ -0,0 +1,28 @@
+version: '3.8'
+
+services:
+  backend:
+    build:
+      context: ./reading-platform-backend
+    container_name: kindergarten-backend
+    restart: unless-stopped
+    ports:
+      - "3001:3001"
+    environment:
+      - PORT=3001
+      - NODE_ENV=production
+      - DATABASE_URL=file:/app/prisma/dev.db
+      - JWT_SECRET=${JWT_SECRET:-change-this-secret}
+      - JWT_EXPIRES_IN=7d
+      - FRONTEND_URL=http://localhost:8080
+      - PRISMA_QUERY_ENGINE_LIBRARY=/app/node_modules/.prisma/client/libquery_engine-linux-musl-openssl-3.0.x.so.node
+
+  frontend:
+    build:
+      context: ./reading-platform-frontend
+    container_name: kindergarten-frontend
+    restart: unless-stopped
+    ports:
+      - "8080:80"
+    depends_on:
+      - backend