📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/tailwindcss/README.md

@@ -0,0 +1,40 @@
+<p align="center">
+  <a href="https://tailwindcss.com" target="_blank">
+    <picture>
+      <source media="(prefers-color-scheme: dark)" srcset="https://raw.githubusercontent.com/tailwindlabs/tailwindcss/HEAD/.github/logo-dark.svg">
+      <source media="(prefers-color-scheme: light)" srcset="https://raw.githubusercontent.com/tailwindlabs/tailwindcss/HEAD/.github/logo-light.svg">
+      <img alt="Tailwind CSS" src="https://raw.githubusercontent.com/tailwindlabs/tailwindcss/HEAD/.github/logo-light.svg" width="350" height="70" style="max-width: 100%;">
+    </picture>
+  </a>
+</p>
+
+<p align="center">
+  A utility-first CSS framework for rapidly building custom user interfaces.
+</p>
+
+<p align="center">
+    <a href="https://github.com/tailwindlabs/tailwindcss/actions"><img src="https://img.shields.io/github/actions/workflow/status/tailwindlabs/tailwindcss/ci.yml?branch=main" alt="Build Status"></a>
+    <a href="https://www.npmjs.com/package/tailwindcss"><img src="https://img.shields.io/npm/dt/tailwindcss.svg" alt="Total Downloads"></a>
+    <a href="https://github.com/tailwindcss/tailwindcss/releases"><img src="https://img.shields.io/npm/v/tailwindcss.svg" alt="Latest Release"></a>
+    <a href="https://github.com/tailwindcss/tailwindcss/blob/main/LICENSE"><img src="https://img.shields.io/npm/l/tailwindcss.svg" alt="License"></a>
+</p>
+
+---
+
+## Documentation
+
+For full documentation, visit [tailwindcss.com](https://tailwindcss.com/).
+
+## Community
+
+For help, discussion about best practices, or any other conversation that would benefit from being searchable:
+
+[Discuss Tailwind CSS on GitHub](https://github.com/tailwindcss/tailwindcss/discussions)
+
+For casual chit-chat with others using the framework:
+
+[Join the Tailwind CSS Discord Server](https://discord.gg/7NF8GNe)
+
+## Contributing
+
+If you're interested in contributing to Tailwind CSS, please read our [contributing docs](https://github.com/tailwindcss/tailwindcss/blob/main/.github/CONTRIBUTING.md) **before submitting a pull request**.