📦 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/@babel/plugin-transform-optional-catch-binding/package.json

@@ -0,0 +1,34 @@
+{
+  "name": "@babel/plugin-transform-optional-catch-binding",
+  "version": "7.28.6",
+  "description": "Compile optional catch bindings",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/babel/babel.git",
+    "directory": "packages/babel-plugin-transform-optional-catch-binding"
+  },
+  "homepage": "https://babel.dev/docs/en/next/babel-plugin-transform-optional-catch-binding",
+  "license": "MIT",
+  "publishConfig": {
+    "access": "public"
+  },
+  "main": "./lib/index.js",
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "@babel/helper-plugin-utils": "^7.28.6"
+  },
+  "peerDependencies": {
+    "@babel/core": "^7.0.0-0"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.28.6",
+    "@babel/helper-plugin-test-runner": "^7.27.1"
+  },
+  "engines": {
+    "node": ">=6.9.0"
+  },
+  "author": "The Babel Team (https://babel.dev/team)",
+  "type": "commonjs"
+}