Add Docker deployment support

- Add Dockerfile for containerization
- Add docker-compose.yml for easy deployment
- Add .dockerignore to optimize build
- Add .env.example for environment configuration
- Add DOCKER_DEPLOY.md with comprehensive deployment guide

Support for:
- Local Docker deployment
- Cloud platforms (Render, Railway, Fly.io, GCP, AWS)
- Persistent storage configuration
- Health checks and monitoring

Dockerfile

@@ -0,0 +1,23 @@
+# 使用官方 Node.js 运行时作为基础镜像
+FROM node:24-alpine
+
+# 设置工作目录
+WORKDIR /app
+
+# 复制 package.json 和 package-lock.json
+COPY package*.json ./
+
+# 安装项目依赖
+RUN npm ci --only=production
+
+# 复制项目文件
+COPY . .
+
+# 暴露端口（默认3000，可通过环境变量覆盖）
+EXPOSE 3000
+
+# 设置环境变量
+ENV NODE_ENV=production
+
+# 启动应用
+CMD ["node", "server.js"]