feat(im): 添加即时消息SDK核心功能实现

- 实现了聊天消息发送功能，支持文本、图片、视频、音频、文件等多种消息类型
- 集成了文件上传下载功能，支持多媒体文件的传输和管理
- 添加了群组管理功能，包括创建群组、成员管理、权限控制等操作
- 实现了好友系统，支持好友添加、删除、分组等功能
- 集成了黑名单管理，提供用户屏蔽和解除屏蔽功能
- 添加了会话管理功能，支持对话列表、未读消息统计等
- 实现了历史消息查询和搜索功能
- 添加了实时连接状态管理和自动重连机制

packages/im/src/ImSDK.ts

@@ -312,6 +312,17 @@ export const ImSDK = {
     client.addListener({
       onConnected: () => {
         _syncHistoryForAllConversations().catch(() => {})
+        // Auto-register push token if Push module is installed and a token is pending
+        import('@xuqm/rn-push')
+          .then(({ PushSDK }) => {
+            const pending = PushSDK.getPendingToken?.()
+            if (pending) {
+              PushSDK.registerToken(userId, pending.token, pending.vendor).catch(() => {})
+            }
+          })
+          .catch(() => {
+            // Push module not installed — ignore gracefully
+          })
       },
     })
     void client.connect()
@@ -1096,6 +1107,12 @@ export const ImSDK = {
     return normalized
   },
 
+  /**
+   * Subscribe to conversation list changes.
+   * Returns the current conversation list immediately via the callback,
+   * then invokes the callback again whenever the list changes.
+   * @returns An unsubscribe function.
+   */
   subscribeConversations(callback: (conversations: ConversationData[]) => void): () => void {
     if (!ImDatabase.isInitialized()) {
       conversationListeners.add(callback)

packages/push/src/PushSDK.ts

@@ -40,6 +40,21 @@ export const PushSDK = {
     await registerPendingToken()
   },
 
+  /**
+   * Cache a device token without immediately registering it.
+   * Call this when the native layer receives a token before the user is logged in.
+   */
+  setPendingToken(token: string, vendor?: PushVendor): void {
+    pendingToken = { token, vendor }
+  },
+
+  /**
+   * Get the currently cached pending token, if any.
+   */
+  getPendingToken(): PendingDeviceToken | null {
+    return pendingToken
+  },
+
   async setDeviceToken(token: string, vendor?: PushVendor): Promise<void> {
     pendingToken = { token, vendor }
     await registerPendingToken()
@@ -102,6 +117,7 @@ export const PushSDK = {
         osVersion: device.osVersion,
       },
     })
+    pendingToken = null
   },
 
   async unregisterToken(userId: string): Promise<void> {