修复：loadWhispers 加 Accept: application/json header

- 确保控制器返回 JSON 而不是 HTML 视图
- 解决名片弹窗查看私聊报网络异常的问题

resources/views/chat/frame.blade.php

@@ -221,7 +221,9 @@
     
         async loadWhispers() {
             try {
-                const res = await fetch('/command/whispers/' + encodeURIComponent(this.userInfo.username));
+                const res = await fetch('/command/whispers/' + encodeURIComponent(this.userInfo.username), {
+                    headers: { 'Accept': 'application/json' }
+                });
                 const data = await res.json();
                 if (data.status === 'success') {
                     this.whisperList = data.messages;