feat(ui): implement keyword highlighting and improve search experience

- Add keyword highlighting in `PostCard` and `PostContentRenderer` using `HighlightText`.
- Implement smart excerpt logic in `PostCard` to show relevant context around search keywords.
- Update `SearchBar` styles for better visual feedback and consistency.
- Enhance `SearchScreen` with modern tab variants and improved tag styling.
- Add support for updating group descriptions in `GroupInfoScreen` and `GroupService`.
- Refactor various UI components for improved layout stability and typography.

src/screens/message/GroupInfoScreen.tsx

@@ -297,6 +297,11 @@ const GroupInfoScreen: React.FC = () => {
         await groupService.setGroupAvatar(groupId, editAvatar);
       }
 
+      // 如果描述有变化，更新群描述
+      if (editDescription !== (group?.description || '')) {
+        await groupService.setGroupDescription(groupId, editDescription.trim());
+      }
+
       // 重新获取群信息
       const updatedGroup = await groupManager.getGroup(groupId, true);
       setGroup(updatedGroup);

src/screens/message/components/ChatScreen/styles.ts

@@ -297,7 +297,7 @@ export function createChatScreenStyles(colors: AppColors, dynamicStyles?: {
   },
   senderName: {
     fontSize: 14,
-    color: colors.chat.textSecondary, // 使用主题次要文字颜色
+    color: textPrimary,
     marginBottom: 4,
     marginLeft: 4,
     fontWeight: '600',