📦 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/get-own-enumerable-property-symbols/CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
+
+### [3.0.2](https://github.com/mightyiam/get-own-enumerable-property-symbols/compare/v3.0.1...v3.0.2) (2019-12-10)
+
+
+### Bug Fixes
+
+* add missing license file ([dbf11c2](https://github.com/mightyiam/get-own-enumerable-property-symbols/commit/dbf11c2b705dcfb42d6ac291f6608adb14ed6fd3)), closes [#87](https://github.com/mightyiam/get-own-enumerable-property-symbols/issues/87)
+
+### [3.0.1](https://github.com/mightyiam/get-own-enumerable-property-symbols/compare/v3.0.0...v3.0.1) (2019-10-04)

frontend/node_modules/get-own-enumerable-property-symbols/LICENSE

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+Copyright (c) 2019, Shahar Or
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.

frontend/node_modules/get-own-enumerable-property-symbols/README.md

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+# get-own-enumerable-property-symbols [![Build Status](https://travis-ci.org/mightyiam/get-own-enumerable-property-symbols.svg?branch=master)](https://travis-ci.org/mightyiam/get-own-enumerable-property-symbols)
+
+Returns an array of all *enumerable* symbol properties found directly upon a given object.
+
+Similar to [`Object.getOwnPropertySymbols`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols)
+but only [enumerable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties) keys.
+
+```js
+import getOwnEnumPropSymbols from 'get-own-enumerable-property-symbols'
+
+getOwnEnumPropSymbols({ [Symbol()]: undefined })
+// [Symbol()]
+getOwnEnumPropSymbols(Object.defineProperty({}, Symbol(), {enumerable: false}))
+// []
+```

frontend/node_modules/get-own-enumerable-property-symbols/lib/index.d.ts

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+declare const _default: (object: object) => symbol[];
+export default _default;

frontend/node_modules/get-own-enumerable-property-symbols/lib/index.js

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+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = (object) => Object
+    .getOwnPropertySymbols(object)
+    .filter((keySymbol) => Object.prototype.propertyIsEnumerable.call(object, keySymbol));
+//# sourceMappingURL=index.js.map

frontend/node_modules/get-own-enumerable-property-symbols/lib/index.js.map

@@ -0,0 +1 @@
+{"version":3,"file":"index.js","sourceRoot":"","sources":["../src/index.ts"],"names":[],"mappings":";;AAAA,kBAAe,CAAC,MAAc,EAAY,EAAE,CAAC,MAAM;KAChD,qBAAqB,CAAC,MAAM,CAAC;KAC7B,MAAM,CAAC,CAAC,SAAS,EAAW,EAAE,CAAC,MAAM,CAAC,SAAS,CAAC,oBAAoB,CAAC,IAAI,CAAC,MAAM,EAAE,SAAS,CAAC,CAAC,CAAA"}

frontend/node_modules/get-own-enumerable-property-symbols/package.json

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+{
+  "name": "get-own-enumerable-property-symbols",
+  "version": "3.0.2",
+  "description": "Returns an array of all enumerable symbol properties found directly upon a given object",
+  "main": "lib/index.js",
+  "types": "lib/index.d.ts",
+  "files": [
+    "lib/index.d.ts",
+    "lib/index.js",
+    "lib/index.js.map"
+  ],
+  "scripts": {
+    "release": "standard-version",
+    "lint": "eslint --ext .ts .",
+    "transpile": "tsc",
+    "unit": "node lib/test.js",
+    "test": "run-s lint transpile unit"
+  },
+  "standard": {
+    "ignore": [
+      "lib"
+    ]
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/mightyiam/get-own-enumerable-property-symbols.git"
+  },
+  "keywords": [
+    "get",
+    "enumerable",
+    "symbol",
+    "property",
+    "key",
+    "object"
+  ],
+  "author": "Shahar Or <mightyiampresence@gmail.com> (mightyiam)",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/mightyiam/get-own-enumerable-property-symbols/issues"
+  },
+  "husky": {
+    "hooks": {
+      "commit-msg": "commitlint -E HUSKY_GIT_PARAMS",
+      "pre-commit": "npm test"
+    }
+  },
+  "homepage": "https://github.com/mightyiam/get-own-enumerable-property-symbols#readme",
+  "devDependencies": {
+    "@commitlint/cli": "^8.2.0",
+    "@commitlint/config-conventional": "^8.2.0",
+    "@commitlint/travis-cli": "^8.2.0",
+    "@types/node": "^12.12.11",
+    "@typescript-eslint/eslint-plugin": "^2.8.0",
+    "eslint": "^6.6.0",
+    "eslint-config-standard-with-typescript": "^11.0.1",
+    "eslint-plugin-import": "^2.18.2",
+    "eslint-plugin-node": "^10.0.0",
+    "eslint-plugin-promise": "^4.2.1",
+    "eslint-plugin-standard": "^4.0.1",
+    "husky": "^3.1.0",
+    "npm-run-all": "^4.1.5",
+    "standard-version": "^7.0.1",
+    "tsconfigs": "^4.0.1",
+    "typescript": "^3.7.2"
+  },
+  "eslintIgnore": [
+    "*.d.ts"
+  ]
+}