feat(message): implement message search functionality

Add ability to search messages within a specific conversation. This includes:
- New `MessageSearchScreen` for displaying search results.
- `MessageRepository.searchByConversation` to query messages by keyword and conversation ID.
- Integration of search entry points in `GroupInfoScreen` and `PrivateChatInfoScreen`.
- Support for scrolling to a specific message sequence (`scrollToSeq`) when navigating from search results.
- Enhanced `HighlightText` component to support custom highlight styles.

feat(message): implement message search functionality

src/components/common/HighlightText.tsx

@@ -5,9 +5,10 @@ interface HighlightTextProps {
   text: string;
   keyword: string;
   style?: StyleProp<TextStyle>;
+  highlightStyle?: StyleProp<TextStyle>;
 }
 
-const HighlightText: React.FC<HighlightTextProps> = ({ text, keyword, style }) => {
+const HighlightText: React.FC<HighlightTextProps> = ({ text, keyword, style, highlightStyle }) => {
   const parts = useMemo(() => {
     if (!text || !keyword) return [{ text, highlight: false }];
 
@@ -37,12 +38,10 @@ const HighlightText: React.FC<HighlightTextProps> = ({ text, keyword, style }) =
   }, [text, keyword]);
 
   return (
-    <Text>
+    <Text style={style}>
       {parts.map((part, i) =>
         part.highlight ? (
-          <Text key={i} style={style}>
-            {part.text}
-          </Text>
+          <Text key={i} style={highlightStyle}>{part.text}</Text>
         ) : (
           <Text key={i}>{part.text}</Text>
         )