feat(message): implement incremental sync and atomic unread updates

Refactor the messaging system to improve synchronization efficiency and state consistency.

- Implement incremental message synchronization using sequence numbers (seq) to reduce payload size.
- Add `markAllAsRead` batch API support to optimize read receipt processing.
- Introduce atomic state updates in `useMessageStore` to prevent inconsistent UI rendering during unread count changes.
- Implement notification deduplication in `WSMessageHandler` to prevent duplicate unread increments during reconnection.
- Optimize `MessageSyncService` to prioritize incremental sync over full snapshots when local data exists.
- Refactor `ReadReceiptManager` to use optimistic updates with proper rollback mechanisms.
- Fix minor UI issues in `SettingsScreen` and `PrivacySettingsScreen` related to theme picker z-index and style application.

src/stores/message/index.ts

@@ -24,7 +24,6 @@ export type { MessageState, MessageActions, MessageStore } from './store';
 // ==================== 类型导出 ====================
 // 从 types.ts 导出所有类型
 export type {
-  MessageManagerState,
   ReadStateRecord,
   MessageManagerConversationListDeps,
   HandleNewMessageOptions,