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/database/core/DatabaseConfig.ts

@@ -0,0 +1,14 @@
+export const DB_CONFIG = {
+  MAX_RETRIES: 4,
+  WEB_RETRY_DELAY_BASE: 500,
+  NATIVE_RETRY_DELAY: 100,
+  WEB_CLOSE_DELAY: 300,
+  WEB_FINAL_CLOSE_DELAY: 200,
+  LOCK_PREFIX: 'db-',
+  DEFAULT_DB_NAME: 'carrot_bbs.db',
+  DB_NAME_PREFIX: 'carrot_bbs_',
+} as const;
+
+export const getDbName = (userId: string | null): string => {
+  return userId ? `${DB_CONFIG.DB_NAME_PREFIX}${userId}.db` : DB_CONFIG.DEFAULT_DB_NAME;
+};