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/components/common/AdaptiveLayout.tsx

@@ -22,6 +22,7 @@ import {
   useBreakpointGTE,
   FineBreakpointKey,
 } from '../../hooks/useResponsive';
+import { blurActiveElement } from '../../infrastructure/platform';
 
 export interface AdaptiveLayoutProps {
   /** 主内容区 */
@@ -160,9 +161,8 @@ export function AdaptiveLayout({
   // 抽屉动画
   useEffect(() => {
     if (isDrawerOpen) {
-      if (Platform.OS === 'web') {
-        const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-        active?.blur?.();
+      if (isDrawerOpen) {
+        blurActiveElement();
       }
       Animated.parallel([
         Animated.timing(slideAnim, {

src/components/common/AppDialogHost.tsx

@@ -6,6 +6,7 @@ import { LinearGradient } from 'expo-linear-gradient';
 
 import { bindDialogListener, DialogPayload } from '../../services/dialogService';
 import { borderRadius, shadows, spacing, useAppColors, type AppColors } from '../../theme';
+import { blurActiveElement } from '../../infrastructure/platform';
 
 function createDialogHostStyles(colors: AppColors) {
   return StyleSheet.create({
@@ -93,12 +94,6 @@ function createDialogHostStyles(colors: AppColors) {
   });
 }
 
-const blurActiveElementOnWeb = () => {
-  if (Platform.OS !== 'web') return;
-  const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-  active?.blur?.();
-};
-
 const AppDialogHost: React.FC = () => {
   const [dialog, setDialog] = useState<DialogPayload | null>(null);
   const colors = useAppColors();
@@ -113,7 +108,7 @@ const AppDialogHost: React.FC = () => {
 
   useEffect(() => {
     if (dialog) {
-      blurActiveElementOnWeb();
+      blurActiveElement();
     }
   }, [dialog]);
 

src/components/common/ImageGallery.tsx

@@ -33,6 +33,7 @@ import { MaterialCommunityIcons } from '@expo/vector-icons';
 import * as MediaLibrary from 'expo-media-library';
 import { File, Paths } from 'expo-file-system';
 import { spacing, borderRadius, fontSizes } from '../../theme';
+import { blurActiveElement } from '../../infrastructure/platform';
 
 const { width: SCREEN_WIDTH, height: SCREEN_HEIGHT } = Dimensions.get('window');
 
@@ -127,10 +128,7 @@ export const ImageGallery: React.FC<ImageGalleryProps> = ({
   // 打开/关闭时重置状态
   useEffect(() => {
     if (visible) {
-      if (Platform.OS === 'web') {
-        const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-        active?.blur?.();
-      }
+      blurActiveElement();
       setCurrentIndex(initialIndex);
       setShowControls(true);
       setError(false);

src/components/common/VideoPlayerModal.tsx

@@ -18,6 +18,7 @@ import { VideoView, useVideoPlayer } from 'expo-video';
 import { MaterialCommunityIcons } from '@expo/vector-icons';
 import { useSafeAreaInsets } from 'react-native-safe-area-context';
 import { spacing, fontSizes, borderRadius } from '../../theme';
+import { blurActiveElement } from '../../infrastructure/platform';
 
 const { width: SCREEN_WIDTH, height: SCREEN_HEIGHT } = Dimensions.get('window');
 
@@ -81,9 +82,8 @@ export const VideoPlayerModal: React.FC<VideoPlayerModalProps> = ({
   onClose,
 }) => {
   useEffect(() => {
-    if (visible && Platform.OS === 'web') {
-      const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-      active?.blur?.();
+    if (visible) {
+      blurActiveElement();
     }
   }, [visible]);