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/stores/message/services/MessageSendService.ts

@@ -9,7 +9,7 @@
 
 import type { MessageResponse, MessageSegment, ConversationResponse } from '../../../types/dto';
 import { messageService } from '../../../services/messageService';
-import { saveMessage } from '../../../services/database';
+import { messageRepository } from '@/database';
 import type { IMessageSendService } from '../types';
 import { useMessageStore, mergeMessagesById } from '../store';
 
@@ -64,7 +64,7 @@ export class MessageSendService implements IMessageSendService {
           .map((s: any) => s.data?.text || '')
           .join('') || '';
         
-        saveMessage({
+        messageRepository.saveMessage({
           id: response.id,
           conversationId,
           senderId: currentUserId || '',