📦 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/wrappy/LICENSE

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+The ISC License
+
+Copyright (c) Isaac Z. Schlueter and Contributors
+
+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/wrappy/README.md

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+# wrappy
+
+Callback wrapping utility
+
+## USAGE
+
+```javascript
+var wrappy = require("wrappy")
+
+// var wrapper = wrappy(wrapperFunction)
+
+// make sure a cb is called only once
+// See also: http://npm.im/once for this specific use case
+var once = wrappy(function (cb) {
+  var called = false
+  return function () {
+    if (called) return
+    called = true
+    return cb.apply(this, arguments)
+  }
+})
+
+function printBoo () {
+  console.log('boo')
+}
+// has some rando property
+printBoo.iAmBooPrinter = true
+
+var onlyPrintOnce = once(printBoo)
+
+onlyPrintOnce() // prints 'boo'
+onlyPrintOnce() // does nothing
+
+// random property is retained!
+assert.equal(onlyPrintOnce.iAmBooPrinter, true)
+```

frontend/node_modules/wrappy/package.json

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+{
+  "name": "wrappy",
+  "version": "1.0.2",
+  "description": "Callback wrapping utility",
+  "main": "wrappy.js",
+  "files": [
+    "wrappy.js"
+  ],
+  "directories": {
+    "test": "test"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "tap": "^2.3.1"
+  },
+  "scripts": {
+    "test": "tap --coverage test/*.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/npm/wrappy"
+  },
+  "author": "Isaac Z. Schlueter <i@izs.me> (http://blog.izs.me/)",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/npm/wrappy/issues"
+  },
+  "homepage": "https://github.com/npm/wrappy"
+}

frontend/node_modules/wrappy/wrappy.js

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+// Returns a wrapper function that returns a wrapped callback
+// The wrapper function should do some stuff, and return a
+// presumably different callback function.
+// This makes sure that own properties are retained, so that
+// decorations and such are not lost along the way.
+module.exports = wrappy
+function wrappy (fn, cb) {
+  if (fn && cb) return wrappy(fn)(cb)
+
+  if (typeof fn !== 'function')
+    throw new TypeError('need wrapper function')
+
+  Object.keys(fn).forEach(function (k) {
+    wrapper[k] = fn[k]
+  })
+
+  return wrapper
+
+  function wrapper() {
+    var args = new Array(arguments.length)
+    for (var i = 0; i < args.length; i++) {
+      args[i] = arguments[i]
+    }
+    var ret = fn.apply(this, args)
+    var cb = args[args.length-1]
+    if (typeof ret === 'function' && ret !== cb) {
+      Object.keys(cb).forEach(function (k) {
+        ret[k] = cb[k]
+      })
+    }
+    return ret
+  }
+}