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/business/QRCodeScanner.tsx

@@ -13,6 +13,7 @@ import { useRouter } from 'expo-router';
 import { MaterialCommunityIcons } from '@expo/vector-icons';
 import * as hrefs from '../../navigation/hrefs';
 import { spacing, fontSizes, borderRadius, useAppColors, type AppColors } from '../../theme';
+import { blurActiveElement } from '../../infrastructure/platform';
 
 const { width, height } = Dimensions.get('window');
 
@@ -156,9 +157,8 @@ const QRCodeScannerWeb: React.FC<QRCodeScannerProps> = ({ visible, onClose }) =>
   const styles = useMemo(() => createQrScannerStyles(themeColors), [themeColors]);
 
   useEffect(() => {
-    if (visible && Platform.OS === 'web') {
-      const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-      active?.blur?.();
+    if (visible) {
+      blurActiveElement();
     }
   }, [visible]);
 

src/components/business/ReportDialog/ReportDialog.tsx

@@ -21,6 +21,7 @@ import { MaterialCommunityIcons } from '@expo/vector-icons';
 import { useAppColors } from '../../../theme';
 import { spacing, borderRadius, fontSizes, shadows } from '../../../theme';
 import reportService, { ReportReason, ReportTargetType, REPORT_REASONS } from '../../../services/reportService';
+import { blurActiveElement } from '../../../infrastructure/platform';
 import Text from '../../common/Text';
 
 export interface ReportDialogProps {
@@ -63,9 +64,8 @@ const ReportDialog: React.FC<ReportDialogProps> = ({
   const targetConfig = TARGET_CONFIG[targetType];
 
   useEffect(() => {
-    if (visible && Platform.OS === 'web') {
-      const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
-      active?.blur?.();
+    if (visible) {
+      blurActiveElement();
     }
   }, [visible]);