📦 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-jest/docs/rules/prefer-strict-equal.md

@@ -0,0 +1,24 @@
+# Suggest using `toStrictEqual()` (`prefer-strict-equal`)
+
+`toStrictEqual` not only checks that two objects contain the same data but also
+that they have the same structure. It is common to expect objects to not only
+have identical values but also to have identical keys. A stricter equality will
+catch cases where two objects do not have identical keys.
+
+## Rule details
+
+This rule triggers a warning if `toEqual()` is used to assert equality.
+
+### Default configuration
+
+The following pattern is considered warning:
+
+```js
+expect({ a: 'a', b: undefined }).toEqual({ a: 'a' }); // true
+```
+
+The following pattern is not warning:
+
+```js
+expect({ a: 'a', b: undefined }).toStrictEqual({ a: 'a' }); // false
+```