feat: 初始化孕育无忧全栈项目基础代码结构

完成项目初始搭建，包含后端FastAPI+MongoDB服务、前端React+Vite项目的完整基础结构，添加各类配置文件与依赖清单，涵盖核心业务初始框架。

frontend/Dockerfile

@@ -0,0 +1,20 @@
+# Build stage
+FROM node:20-alpine AS build
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+
+# Serve stage
+FROM nginx:alpine
+
+COPY --from=build /app/dist /usr/share/nginx/html
+# nginx config will be mounted via docker-compose
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]