📦 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/memo-parser/README.md

@@ -0,0 +1,21 @@
+# eslint-plugin-import/memo-parser
+
+## NOTE
+
+This used to improve performance, but as of ESLint 5 and v2 of this plugin, it seems to just consume a bunch of memory and slightly increase lint times.
+
+**Not recommended for use at this time!**
+
+This parser is just a memoizing wrapper around some actual parser.
+
+To configure, just add your _actual_ parser to the `parserOptions`, like so:
+
+```yaml
+parser: eslint-plugin-import/memo-parser
+# parser: babel-eslint
+
+parserOptions:
+  parser: babel-eslint
+  sourceType: module
+  ecmaVersion: 6
+```