refactor(icons): 迁移公共模块图标到 lucide-react

- constants/importanceLevels.js: 重要性等级图标
- constants/notificationTypes.js: 通知类型图标
- contexts/NotificationContext.js: 通知上下文图标
- layouts/components/BackToTopButton.js: 返回顶部按钮
- utils/priceFormatters.js: 价格格式化图标
- variables/general.js: 通用变量图标

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/layouts/components/BackToTopButton.js

@@ -1,7 +1,7 @@
 // src/layouts/components/BackToTopButton.js
 import React, { useState, useEffect, useCallback, useRef, memo } from 'react';
 import { IconButton } from '@chakra-ui/react';
-import { FiArrowUp } from 'react-icons/fi';
+import { ArrowUp } from 'lucide-react';
 
 /**
  * 返回顶部按钮组件
@@ -69,7 +69,7 @@ const BackToTopButton = memo(({
 
     return (
         <IconButton
-            icon={<FiArrowUp />}
+            icon={<ArrowUp size={20} />}
             position="fixed"
             bottom={position.bottom}
             right={position.right}