📦 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/core-js/es/date/get-year.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.get-year');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Date', 'getYear');

frontend/node_modules/core-js/es/date/index.js

@@ -0,0 +1,12 @@
+'use strict';
+require('../../modules/es.date.get-year');
+require('../../modules/es.date.now');
+require('../../modules/es.date.set-year');
+require('../../modules/es.date.to-gmt-string');
+require('../../modules/es.date.to-iso-string');
+require('../../modules/es.date.to-json');
+require('../../modules/es.date.to-string');
+require('../../modules/es.date.to-primitive');
+var path = require('../../internals/path');
+
+module.exports = path.Date;

frontend/node_modules/core-js/es/date/now.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.now');
+var path = require('../../internals/path');
+
+module.exports = path.Date.now;

frontend/node_modules/core-js/es/date/set-year.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.set-year');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Date', 'setYear');

frontend/node_modules/core-js/es/date/to-gmt-string.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.to-gmt-string');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Date', 'toGMTString');

frontend/node_modules/core-js/es/date/to-iso-string.js

@@ -0,0 +1,6 @@
+'use strict';
+require('../../modules/es.date.to-iso-string');
+require('../../modules/es.date.to-json');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Date', 'toISOString');

frontend/node_modules/core-js/es/date/to-json.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.to-json');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Date', 'toJSON');

frontend/node_modules/core-js/es/date/to-primitive.js

@@ -0,0 +1,6 @@
+'use strict';
+require('../../modules/es.date.to-primitive');
+var uncurryThis = require('../../internals/function-uncurry-this');
+var toPrimitive = require('../../internals/date-to-primitive');
+
+module.exports = uncurryThis(toPrimitive);

frontend/node_modules/core-js/es/date/to-string.js

@@ -0,0 +1,5 @@
+'use strict';
+require('../../modules/es.date.to-string');
+var uncurryThis = require('../../internals/function-uncurry-this');
+
+module.exports = uncurryThis(Date.prototype.toString);