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/LongPressMenu.tsx

@@ -20,6 +20,7 @@ import { LongPressMenuProps } from './types';
 import { RECALL_TIME_LIMIT } from './constants';
 import { extractTextFromSegments, ImageSegmentData } from '../../../../types/dto';
 import { isStickerExists, addStickerFromUrl } from '../../../../services/stickerService';
+import { blurActiveElement } from '../../../../infrastructure/platform';
 
 const { width: SCREEN_WIDTH, height: SCREEN_HEIGHT } = Dimensions.get('window');
 
@@ -37,16 +38,11 @@ export const LongPressMenu: React.FC<LongPressMenuProps> = ({
   const styles = useChatScreenStyles();
   const scaleAnimation = useRef(new Animated.Value(0)).current;
   const opacityAnimation = useRef(new Animated.Value(0)).current;
-  const blurActiveElementOnWeb = () => {
-    if (Platform.OS !== 'web') return;
-    const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-    active?.blur?.();
-  };
 
   // 显示动画 - 缩放弹出
   useEffect(() => {
     if (visible) {
-      blurActiveElementOnWeb();
+      blurActiveElement();
       Animated.parallel([
         Animated.spring(scaleAnimation, {
           toValue: 1,
@@ -61,7 +57,7 @@ export const LongPressMenu: React.FC<LongPressMenuProps> = ({
         }),
       ]).start();
     } else {
-      blurActiveElementOnWeb();
+      blurActiveElement();
       Animated.parallel([
         Animated.timing(scaleAnimation, {
           toValue: 0,
@@ -251,12 +247,12 @@ export const LongPressMenu: React.FC<LongPressMenuProps> = ({
       visible={visible}
       transparent
       animationType="none"
-      onShow={blurActiveElementOnWeb}
+      onShow={blurActiveElement}
       onRequestClose={onClose}
     >
       <Pressable
         onPress={() => {
-          blurActiveElementOnWeb();
+          blurActiveElement();
           onClose();
         }}
         style={styles.qqMenuOverlay}