feat(ws): implement sync_required event and message acknowledgement

Add support for a new `sync_required` WebSocket message type to trigger
incremental synchronization of conversations, unread counts, and active
messages. Also implement an `ack` mechanism to acknowledge received
messages.

src/services/core/wsService.ts

@@ -41,7 +41,8 @@ export type WSMessageType =
   | 'call_ended'
   | 'call_peer_muted'
   | 'call_invited'
-  | 'call_answered_elsewhere';
+  | 'call_answered_elsewhere'
+  | 'sync_required';
 
 export interface WSCallIncomingMessage {
   type: 'call_incoming';
@@ -249,6 +250,10 @@ export interface WSGroupRecallMessage {
   message_id: string;
 }
 
+export interface WSSyncRequiredMessage {
+  type: 'sync_required';
+}
+
 export interface WSServerMessage {
   event_id?: number;
   type: string;
@@ -279,7 +284,8 @@ export type WSMessage =
   | WSCallPeerMutedMessage
   | WSCallInvitedMessage
   | WSCallAnsweredElsewhereMessage
-  | WSErrorMessage;
+  | WSErrorMessage
+  | WSSyncRequiredMessage;
 
 type MessageHandler<T extends WSMessage = WSMessage> = (message: T) => void;
 type ConnectionHandler = () => void;
@@ -496,6 +502,9 @@ class WebSocketService {
       case 'call_answered_elsewhere':
         this.handleCallAnsweredElsewhere(payload);
         break;
+      case 'sync_required':
+        this.emit('sync_required', { type: 'sync_required' });
+        break;
       default:
         console.log('Unknown message type:', type);
     }
@@ -886,6 +895,11 @@ class WebSocketService {
     this.ws.send(JSON.stringify(message));
   }
 
+  // 发送 ACK 确认（fire-and-forget）
+  sendAck(messageId: string): void {
+    this.sendFireAndForget('ack', { message_id: messageId });
+  }
+
   // 通过WebSocket发送
   private sendViaWebSocket(type: string, payload: any): Promise<any> {
     return new Promise((resolve, reject) => {