📦 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/delayed-stream/package.json

@@ -0,0 +1,27 @@
+{
+  "author": "Felix Geisendörfer <felix@debuggable.com> (http://debuggable.com/)",
+  "contributors": [
+    "Mike Atkins <apeherder@gmail.com>"
+  ],
+  "name": "delayed-stream",
+  "description": "Buffers events from a stream until you are ready to handle them.",
+  "license": "MIT",
+  "version": "1.0.0",
+  "homepage": "https://github.com/felixge/node-delayed-stream",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/felixge/node-delayed-stream.git"
+  },
+  "main": "./lib/delayed_stream",
+  "engines": {
+    "node": ">=0.4.0"
+  },
+  "scripts": {
+    "test": "make test"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "fake": "0.2.0",
+    "far": "0.0.1"
+  }
+}