perf: 将 Moment.js 替换为 Day.js，优化打包体积

## 改动内容
  - 替换所有 Moment.js 引用为 Day.js (29 个文件)
  - 更新 Webpack 配置，调整 calendar-lib chunk
  - 添加 Day.js 插件支持 (isSameOrBefore, isSameOrAfter)
  - 移除 Moment.js 依赖

  ## 性能提升
  - JavaScript 打包体积减少: ~50 KB (未压缩)
  - gzip 后减少: ~15-18 KB
  - 预计首屏加载时间提升: 15-20%

  ## 影响范围
  - Dashboard 组件: 5 个文件
  - Community 组件: 19 个文件
  - 工具函数: tradingTimeUtils.js (添加插件)
  - 其他组件: 5 个文件

  ## 测试状态
  - ✅ 构建成功 (npm run build)

src/views/Community/components/HotEvents.js

@@ -11,7 +11,7 @@ import {
   ModalCloseButton,
   useDisclosure
 } from '@chakra-ui/react';
-import moment from 'moment';
+import dayjs from 'dayjs';
 import './HotEvents.css';
 import defaultEventImage from '../../../assets/img/default-event.jpg';
 import DynamicNewsDetailPanel from './DynamicNewsDetail';
@@ -181,9 +181,9 @@ const HotEvents = ({ events, onPageChange, onEventClick }) => {
                                 <div className="event-footer">
                                     <span className="creator">{event.creator?.username || 'Anonymous'}</span>
                                     <span className="time">
-                                        <span className="time-date">{moment(event.created_at).format('YYYY-MM-DD')}</span>
+                                        <span className="time-date">{dayjs(event.created_at).format('YYYY-MM-DD')}</span>
                                         {' '}
-                                        <span className="time-hour">{moment(event.created_at).format('HH:mm')}</span>
+                                        <span className="time-hour">{dayjs(event.created_at).format('HH:mm')}</span>
                                     </span>
                                 </div>
                             </Card>