📦 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/eslint-plugin-react/lib/rules/jsx-uses-react.js

@@ -0,0 +1,52 @@
+/**
+ * @fileoverview Prevent React to be marked as unused
+ * @author Glen Mailer
+ */
+
+'use strict';
+
+const pragmaUtil = require('../util/pragma');
+const docsUrl = require('../util/docsUrl');
+const markVariableAsUsed = require('../util/eslint').markVariableAsUsed;
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  // eslint-disable-next-line eslint-plugin/prefer-message-ids -- https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/issues/292
+  meta: {
+    docs: {
+      description: 'Disallow React to be incorrectly marked as unused',
+      category: 'Best Practices',
+      recommended: true,
+      url: docsUrl('jsx-uses-react'),
+    },
+    schema: [],
+  },
+
+  create(context) {
+    const pragma = pragmaUtil.getFromContext(context);
+    const fragment = pragmaUtil.getFragmentFromContext(context);
+
+    /**
+     * @param {ASTNode} node
+     * @returns {void}
+     */
+    function handleOpeningElement(node) {
+      markVariableAsUsed(pragma, node, context);
+    }
+    // --------------------------------------------------------------------------
+    // Public
+    // --------------------------------------------------------------------------
+
+    return {
+      JSXOpeningElement: handleOpeningElement,
+      JSXOpeningFragment: handleOpeningElement,
+      JSXFragment(node) {
+        markVariableAsUsed(fragment, node, context);
+      },
+    };
+  },
+};