- Add schema for im_conversations and im_messages tables
- ConversationModel/MessageModel: WatermelonDB ORM models
- ImDatabase: init/saveMessage/getMessages/getConversations/markRead/bulkSave
- ImSDK: fetchHistory/fetchGroupHistory read local DB first, cache server results
- ImSDK: incoming WebSocket messages auto-saved to local DB
- ImSDK: new listConversations() and markRead() public APIs
- @nozbe/watermelondb >=0.27.0 added as peer dependency
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>