refactor(database): migrate to new modular database layer and unify data access

- Remove legacy database.ts, LocalDataSource.ts, and MessageRepository.ts
- Create new src/database/ module with messageRepository, userCacheRepository, conversationRepository, and groupCacheRepository
- Update all consumers to import from @/database instead of services/database
- Add web platform blur handling for modal components to fix focus issues
- Flatten SystemMessageItem and NotificationsScreen styles for consistent design
- Add draggable slider in ChatSettingsScreen and dynamic font size support
- Introduce 9 new chat color themes
- Add profile screens for about, terms, and privacy policy with navigation routes
- Add policy links to login and registration screens
- Fix post share URL format from /posts/ to /post/

src/screens/message/MessageListScreen.tsx

@@ -136,6 +136,13 @@ export const MessageListScreen: React.FC = () => {
   const [isSearching, setIsSearching] = useState(false);
   const [activeSearchTab, setActiveSearchTab] = useState<'chat' | 'user'>('chat');
   const [actionMenuVisible, setActionMenuVisible] = useState(false);
+
+  useEffect(() => {
+    if (actionMenuVisible && Platform.OS === 'web') {
+      const active = (globalThis as any)?.document?.activeElement as { blur?: () => void } | undefined;
+      active?.blur?.();
+    }
+  }, [actionMenuVisible]);
   const [scannerVisible, setScannerVisible] = useState(false);
 
   // 系统通知显示状态 - 用于在移动端显示通知页面