📦 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/encodeurl/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "encodeurl",
+  "description": "Encode a URL to a percent-encoded form, excluding already-encoded sequences",
+  "version": "2.0.0",
+  "contributors": [
+    "Douglas Christopher Wilson <doug@somethingdoug.com>"
+  ],
+  "license": "MIT",
+  "keywords": [
+    "encode",
+    "encodeurl",
+    "url"
+  ],
+  "repository": "pillarjs/encodeurl",
+  "devDependencies": {
+    "eslint": "5.11.1",
+    "eslint-config-standard": "12.0.0",
+    "eslint-plugin-import": "2.14.0",
+    "eslint-plugin-node": "7.0.1",
+    "eslint-plugin-promise": "4.0.1",
+    "eslint-plugin-standard": "4.0.0",
+    "istanbul": "0.4.5",
+    "mocha": "2.5.3"
+  },
+  "files": [
+    "LICENSE",
+    "HISTORY.md",
+    "README.md",
+    "index.js"
+  ],
+  "engines": {
+    "node": ">= 0.8"
+  },
+  "scripts": {
+    "lint": "eslint .",
+    "test": "mocha --reporter spec --bail --check-leaks test/",
+    "test-cov": "istanbul cover node_modules/mocha/bin/_mocha -- --reporter dot --check-leaks test/",
+    "test-travis": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly -- --reporter spec --check-leaks test/"
+  }
+}