📦 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/minimalistic-assert/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "minimalistic-assert",
+  "version": "1.0.1",
+  "description": "minimalistic-assert ===",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/calvinmetcalf/minimalistic-assert.git"
+  },
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/calvinmetcalf/minimalistic-assert/issues"
+  },
+  "homepage": "https://github.com/calvinmetcalf/minimalistic-assert"
+}