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/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',