feat: 添加多语言客户端 Docker 支持

- 新增 .NET 客户端 SDK 和 demo 项目
- 添加 Go/Node.js/Python/.NET/SpringBoot2 的 Dockerfile
- Go demo 支持从环境变量读取配置
- 创建 README_DOCKERFILE.md 文档说明 Docker 使用方法
- 更新根目录 README.md 标记 .NET 客户端为已支持

Dockerfile.nodejs

@@ -0,0 +1,27 @@
+# Build stage
+FROM node:18-alpine AS build
+
+WORKDIR /src
+
+# Copy client library
+COPY kenaito-conf-nodejs-client/ ./kenaito-conf-nodejs-client/
+
+# Copy demo project
+COPY kenaito-conf-nodejs-client-demo/ ./kenaito-conf-nodejs-client-demo/
+
+# Install client locally, then demo dependencies
+WORKDIR /src/kenaito-conf-nodejs-client
+RUN npm link
+
+WORKDIR /src/kenaito-conf-nodejs-client-demo
+RUN npm link kenaito-conf && npm install
+
+# Runtime stage
+FROM node:18-alpine
+
+WORKDIR /app
+COPY --from=build /src/kenaito-conf-nodejs-client-demo .
+
+EXPOSE 8083
+
+CMD ["node", "app.js"]