📦 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/ajv-keywords/keywords/index.js

@@ -0,0 +1,22 @@
+'use strict';
+
+module.exports = {
+  'instanceof': require('./instanceof'),
+  range: require('./range'),
+  regexp: require('./regexp'),
+  'typeof': require('./typeof'),
+  dynamicDefaults: require('./dynamicDefaults'),
+  allRequired: require('./allRequired'),
+  anyRequired: require('./anyRequired'),
+  oneRequired: require('./oneRequired'),
+  prohibited: require('./prohibited'),
+  uniqueItemProperties: require('./uniqueItemProperties'),
+  deepProperties: require('./deepProperties'),
+  deepRequired: require('./deepRequired'),
+  formatMinimum: require('./formatMinimum'),
+  formatMaximum: require('./formatMaximum'),
+  patternRequired: require('./patternRequired'),
+  'switch': require('./switch'),
+  select: require('./select'),
+  transform: require('./transform')
+};