📦 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/source-list-map/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "source-list-map",
+  "version": "2.0.1",
+  "description": "Fast line to line SourceMap generator.",
+  "author": "Tobias Koppers @sokra",
+  "main": "lib/index.js",
+  "scripts": {
+    "test": "mocha -R spec"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/webpack/source-list-map.git"
+  },
+  "keywords": [
+    "source-map"
+  ],
+  "files": [
+    "lib"
+  ],
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/webpack/source-list-map/issues"
+  },
+  "homepage": "https://github.com/webpack/source-list-map",
+  "devDependencies": {
+    "mocha": "^2.2.1",
+    "should": "^5.2.0"
+  }
+}