refactor(platform): extract blurActiveElement to infrastructure module

- Centralize duplicated Platform.OS === 'web' blur logic across 16 components
- Add blurActiveElement utility to src/infrastructure/platform module
- Optimize MessageBubble and ImageSegment with React.memo custom comparators
- Add useMemo for computed values in MessageSegmentsRenderer
- Update DTO types with is_system_notice and notice_content fields
- Fix keyboard dismissal order in useChatScreen handleDismiss
- Simplify userStore follow/unfollow state updates
- Remove unnecessary TypeScript type assertions throughout codebase

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

@@ -174,9 +174,9 @@ export const useChatScreen = () => {
       status: (m.status || 'normal') as MessageStatus,
       category: m.category,
       created_at: m.created_at,
-      sender: (m as any).sender,
-      is_system_notice: (m as any).is_system_notice,
-      notice_content: (m as any).notice_content,
+      sender: m.sender,
+      is_system_notice: m.is_system_notice,
+      notice_content: m.notice_content,
     }));
   }, [messageManagerMessages]);
 
@@ -258,7 +258,7 @@ export const useChatScreen = () => {
         setOtherUser(prev => ({ ...(prev || {}), ...other }));
       }
       // 获取对方最后阅读位置
-      setOtherUserLastReadSeq((conversation as any).other_last_read_seq || 0);
+      setOtherUserLastReadSeq(conversation.other_last_read_seq || 0);
     }
   }, [conversation, isGroupChat, currentUserId]);
 
@@ -273,8 +273,8 @@ export const useChatScreen = () => {
         const detail = await userManager.getUserById(String(otherUserId), true);
         if (!detail || cancelled) return;
         setOtherUser(prev => ({ ...(prev || {}), ...detail }));
-        if (typeof (detail as any).is_following_me === 'boolean') {
-          setIsFollowedByOther((detail as any).is_following_me);
+        if (typeof detail.is_following_me === 'boolean') {
+          setIsFollowedByOther(detail.is_following_me);
         } else {
           setIsFollowedByOther(null);
         }
@@ -360,7 +360,7 @@ export const useChatScreen = () => {
   }, [loading, loadingMore, messages.length, scrollToLatest]);
 
   // 新消息跟随策略（Telegram/QQ 风格）：
-  // 仅当“最新端消息 seq 增长”且用户在底部附近时才跟随；
+  // 仅当"最新端消息 seq 增长"且用户在底部附近时才跟随；
   // 历史加载只会增加旧消息，不会提升 latest seq，因此不会触发回底。
   useEffect(() => {
     const currentCount = messages.length;
@@ -371,14 +371,14 @@ export const useChatScreen = () => {
 
     if (loading || loadingMore) return;
     if (latestSeq <= prevLatestSeq) return;
-    if (suppressAutoFollowRef.current) return;
+    if (suppressAutoFollowRef.current || isBrowsingHistoryRef.current || isHistoryLoadingLocked()) return;
     if (!isNearBottom()) return;
 
     const timer = setTimeout(() => {
       scrollToLatest(false, false, 'new-message-follow');
     }, 0);
     return () => clearTimeout(timer);
-  }, [messages, loading, loadingMore, isNearBottom, scrollToLatest]);
+  }, [messages, loading, loadingMore, isNearBottom, scrollToLatest, isHistoryLoadingLocked]);
 
   // 获取当前用户信息
   useEffect(() => {
@@ -559,10 +559,10 @@ export const useChatScreen = () => {
     if (!conversationId) return;
     if (!conversation) return;
 
-    const unreadCount = Number((conversation as any).unread_count || 0);
+    const unreadCount = Number(conversation.unread_count || 0);
     if (unreadCount <= 0) return;
 
-    const latestFromConversation = Number((conversation as any).last_seq || 0);
+    const latestFromConversation = Number(conversation.last_seq || 0);
     const latestFromMessages = messages.length > 0 ? Math.max(...messages.map(m => m.seq || 0)) : 0;
     const targetSeq = Math.max(latestFromConversation, latestFromMessages);
     if (targetSeq <= 0) return;
@@ -1305,8 +1305,8 @@ export const useChatScreen = () => {
 
   // 关闭所有面板
   const handleDismiss = useCallback(() => {
+    Keyboard.dismiss();
     if (activePanel !== 'none') {
-      Keyboard.dismiss();
       setActivePanel('none');
     }
   }, [activePanel]);