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/components/common/AdaptiveLayout.tsx

@@ -15,6 +15,7 @@ import {
   Modal,
   Pressable,
   Dimensions,
+  Platform,
 } from 'react-native';
 import {
   useResponsive,
@@ -159,6 +160,10 @@ 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?.();
+      }
       Animated.parallel([
         Animated.timing(slideAnim, {
           toValue: 1,