- Remove MessageStateManager wrapper layer in favor of direct zustand store
- Move service modules to services/ subdirectory (ConversationOperations, MessageDeduplication, MessageSendService, MessageSyncService, ReadReceiptManager, UserCacheService, WSMessageHandler)
- Add new zustand-based store with subscriptionManager for event handling
- Introduce React hooks for message state (useConversations, useMessages, useUnreadCount, etc.)
- Update exports in index.ts to reflect new module structure
- Deprecate messageManager.ts entry point in favor of message/index.ts
- Maintain backward compatibility with existing MessageManager API
