📦 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/eslint-plugin-import/docs/rules/no-empty-named-blocks.md

@@ -0,0 +1,49 @@
+# import/no-empty-named-blocks
+
+🔧💡 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix) and manually fixable by [editor suggestions](https://eslint.org/docs/latest/use/core-concepts#rule-suggestions).
+
+<!-- end auto-generated rule header -->
+
+Reports the use of empty named import blocks.
+
+## Rule Details
+
+### Valid
+
+```js
+import { mod } from 'mod'
+import Default, { mod } from 'mod'
+```
+
+When using typescript
+
+```js
+import type { mod } from 'mod'
+```
+
+When using flow
+
+```js
+import typeof { mod } from 'mod'
+```
+
+### Invalid
+
+```js
+import {} from 'mod'
+import Default, {} from 'mod'
+```
+
+When using typescript
+
+```js
+import type Default, {} from 'mod'
+import type {} from 'mod'
+```
+
+When using flow
+
+```js
+import typeof {} from 'mod'
+import typeof Default, {} from 'mod'
+```