📦 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/events/History.md

@@ -0,0 +1,118 @@
+# 3.3.0
+
+ - Support EventTarget emitters in `events.once` from Node.js 12.11.0.
+
+   Now you can use the `events.once` function with objects that implement the EventTarget interface. This interface is used widely in
+   the DOM and other web APIs.
+
+   ```js
+   var events = require('events');
+   var assert = require('assert');
+
+   async function connect() {
+     var ws = new WebSocket('wss://example.com');
+     await events.once(ws, 'open');
+     assert(ws.readyState === WebSocket.OPEN);
+   }
+
+   async function onClick() {
+     await events.once(document.body, 'click');
+     alert('you clicked the page!');
+   }
+   ```
+
+# 3.2.0
+
+ - Add `events.once` from Node.js 11.13.0.
+
+   To use this function, Promises must be supported in the environment. Use a polyfill like `es6-promise` if you support older browsers.
+
+# 3.1.0 (2020-01-08)
+
+`events` now matches the Node.js 11.12.0 API.
+
+  - pass through return value in wrapped `emitter.once()` listeners
+
+    Now, this works:
+    ```js
+    emitter.once('myevent', function () { return 1; });
+    var listener = emitter.rawListeners('myevent')[0]
+    assert(listener() === 1);
+    ```
+    Previously, `listener()` would return undefined regardless of the implementation.
+
+    Ported from https://github.com/nodejs/node/commit/acc506c2d2771dab8d7bba6d3452bc5180dff7cf
+
+  - Reduce code duplication in listener type check ([#67](https://github.com/Gozala/events/pull/67) by [@friederbluemle](https://github.com/friederbluemle)).
+  - Improve `emitter.once()` performance in some engines
+
+# 3.0.0 (2018-05-25)
+
+**This version drops support for IE8.** `events` no longer includes polyfills
+for ES5 features. If you need to support older environments, use an ES5 shim
+like [es5-shim](https://npmjs.com/package/es5-shim). Both the shim and sham
+versions of es5-shim are necessary.
+
+  - Update to events code from Node.js 10.x
+    - (semver major) Adds `off()` method
+  - Port more tests from Node.js
+  - Switch browser tests to airtap, making things more reliable
+
+# 2.1.0 (2018-05-25)
+
+  - add Emitter#rawListeners from Node.js v9.4
+
+# 2.0.0 (2018-02-02)
+
+  - Update to events code from node.js 8.x
+    - Adds `prependListener()` and `prependOnceListener()`
+    - Adds `eventNames()` method
+    - (semver major) Unwrap `once()` listeners in `listeners()`
+  - copy tests from node.js
+
+Note that this version doubles the gzipped size, jumping from 1.1KB to 2.1KB,
+due to new methods and runtime performance improvements. Be aware of that when
+upgrading.
+
+# 1.1.1 (2016-06-22)
+
+  - add more context to errors if they are not instanceof Error
+
+# 1.1.0 (2015-09-29)
+
+  - add Emitter#listerCount (to match node v4 api)
+
+# 1.0.2 (2014-08-28)
+
+  - remove un-reachable code
+  - update devDeps
+
+## 1.0.1 / 2014-05-11
+
+  - check for console.trace before using it
+
+## 1.0.0 / 2013-12-10
+
+  - Update to latest events code from node.js 0.10
+  - copy tests from node.js
+
+## 0.4.0 / 2011-07-03 ##
+
+  - Switching to graphquire@0.8.0
+
+## 0.3.0 / 2011-07-03 ##
+
+  - Switching to URL based module require.
+
+## 0.2.0 / 2011-06-10 ##
+
+  - Simplified package structure.
+  - Graphquire for dependency management.
+
+## 0.1.1 / 2011-05-16 ##
+
+  - Unhandled errors are logged via console.error
+
+## 0.1.0 / 2011-04-22 ##
+
+  - Initial release