feat(home): add help center quick operation link

- Add helpCenter.svg and helpCenter_active.svg menu icons for help center navigation
- Add "Help Center" translation strings to English and Chinese i18n files
- Update QuickOperation component to include help center as fourth quick operation
- Implement external link handler that opens help documentation based on current language (zh or en)
- Change grid layout from 3 columns to 4 columns to accommodate new help center card
- Add file header documentation to QuickOperation component
- Help center link redirects to https://docs.redbearai.com/s/{lang}-memorybear with language-specific routing

web/src/i18n/zh.ts

@@ -789,7 +789,8 @@ export const zh = {
 
       memoryConversation: '记忆对话',
       memoryConversationDesc: '记忆对话',
-
+      helpCenter: '帮助中心',
+      helpCenterDesc: '帮助中心',
       memorySummary: '查看记忆摘要',
       memorySummaryDesc: '查看记忆摘要报告',