📦 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/features/symbol/async-dispose.js

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+'use strict';
+module.exports = require('../../full/symbol/async-dispose');

frontend/node_modules/core-js/features/symbol/async-iterator.js

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+'use strict';
+module.exports = require('../../full/symbol/async-iterator');

frontend/node_modules/core-js/features/symbol/custom-matcher.js

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+'use strict';
+module.exports = require('../../full/symbol/custom-matcher');

frontend/node_modules/core-js/features/symbol/description.js

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+'use strict';
+module.exports = require('../../full/symbol/description');

frontend/node_modules/core-js/features/symbol/dispose.js

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+'use strict';
+module.exports = require('../../full/symbol/dispose');

frontend/node_modules/core-js/features/symbol/for.js

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+'use strict';
+module.exports = require('../../full/symbol/for');

frontend/node_modules/core-js/features/symbol/has-instance.js

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+'use strict';
+module.exports = require('../../full/symbol/has-instance');

frontend/node_modules/core-js/features/symbol/index.js

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+'use strict';
+module.exports = require('../../full/symbol');

frontend/node_modules/core-js/features/symbol/is-concat-spreadable.js

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+'use strict';
+module.exports = require('../../full/symbol/is-concat-spreadable');

frontend/node_modules/core-js/features/symbol/is-registered-symbol.js

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+'use strict';
+module.exports = require('../../full/symbol/is-registered-symbol');

frontend/node_modules/core-js/features/symbol/is-registered.js

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+'use strict';
+module.exports = require('../../full/symbol/is-registered');

frontend/node_modules/core-js/features/symbol/is-well-known-symbol.js

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+'use strict';
+module.exports = require('../../full/symbol/is-well-known-symbol');

frontend/node_modules/core-js/features/symbol/is-well-known.js

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+'use strict';
+module.exports = require('../../full/symbol/is-well-known');

frontend/node_modules/core-js/features/symbol/iterator.js

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+'use strict';
+module.exports = require('../../full/symbol/iterator');

frontend/node_modules/core-js/features/symbol/key-for.js

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+'use strict';
+module.exports = require('../../full/symbol/key-for');

frontend/node_modules/core-js/features/symbol/match-all.js

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+'use strict';
+module.exports = require('../../full/symbol/match-all');

frontend/node_modules/core-js/features/symbol/match.js

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+'use strict';
+module.exports = require('../../full/symbol/match');

frontend/node_modules/core-js/features/symbol/matcher.js

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+'use strict';
+module.exports = require('../../full/symbol/matcher');

frontend/node_modules/core-js/features/symbol/metadata-key.js

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+'use strict';
+module.exports = require('../../full/symbol/metadata-key');

frontend/node_modules/core-js/features/symbol/metadata.js

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+'use strict';
+module.exports = require('../../full/symbol/metadata');

frontend/node_modules/core-js/features/symbol/observable.js

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+'use strict';
+module.exports = require('../../full/symbol/observable');

frontend/node_modules/core-js/features/symbol/pattern-match.js

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+'use strict';
+module.exports = require('../../full/symbol/pattern-match');

frontend/node_modules/core-js/features/symbol/replace-all.js

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+'use strict';
+module.exports = require('../../full/symbol/replace-all');

frontend/node_modules/core-js/features/symbol/replace.js

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+'use strict';
+module.exports = require('../../full/symbol/replace');

frontend/node_modules/core-js/features/symbol/search.js

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+'use strict';
+module.exports = require('../../full/symbol/search');

frontend/node_modules/core-js/features/symbol/species.js

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+'use strict';
+module.exports = require('../../full/symbol/species');

frontend/node_modules/core-js/features/symbol/split.js

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+'use strict';
+module.exports = require('../../full/symbol/split');

frontend/node_modules/core-js/features/symbol/to-primitive.js

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+'use strict';
+module.exports = require('../../full/symbol/to-primitive');

frontend/node_modules/core-js/features/symbol/to-string-tag.js

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+'use strict';
+module.exports = require('../../full/symbol/to-string-tag');

frontend/node_modules/core-js/features/symbol/unscopables.js

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+'use strict';
+module.exports = require('../../full/symbol/unscopables');