📦 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/es-abstract/2015/tables/typed-array-objects.js

@@ -0,0 +1,32 @@
+'use strict';
+
+// https://262.ecma-international.org/6.0/#table-49
+
+module.exports = {
+	__proto__: null,
+	name: {
+		__proto__: null,
+		$Int8Array: 'Int8',
+		$Uint8Array: 'Uint8',
+		$Uint8ClampedArray: 'Uint8C',
+		$Int16Array: 'Int16',
+		$Uint16Array: 'Uint16',
+		$Int32Array: 'Int32',
+		$Uint32Array: 'Uint32',
+		$Float32Array: 'Float32',
+		$Float64Array: 'Float64'
+	},
+	size: {
+		__proto__: null,
+		$Int8: 1,
+		$Uint8: 1,
+		$Uint8C: 1,
+		$Int16: 2,
+		$Uint16: 2,
+		$Int32: 4,
+		$Uint32: 4,
+		$Float32: 4,
+		$Float64: 8
+	},
+	choices: '"Int8", "Uint8", "Uint8C", "Int16", "Uint16", "Int32", "Uint32", "Float32", or "Float64"'
+};