修复：前端 headface 引用统一 toLowerCase() 防止大写和 undefined

- 用户列表和发言头像引用加 .toLowerCase()
- 兼容 Redis 缓存中的旧 .GIF 大写数据

resources/views/chat/partials/scripts.blade.php

@@ -139,7 +139,7 @@
             item.className = 'user-item';
             item.dataset.username = username;
 
-            const headface = user.headface || '1.gif';
+            const headface = (user.headface || '1.gif').toLowerCase();
             // VIP 图标和管理员标识
             let badges = '';
             if (user.vip_icon) {
@@ -284,7 +284,7 @@
 
         // 获取发言者头像
         const senderInfo = onlineUsers[msg.from_user];
-        const senderHead = (senderInfo && senderInfo.headface) || '1.gif';
+        const senderHead = ((senderInfo && senderInfo.headface) || '1.gif').toLowerCase();
         const headImg =
             `<img src="/images/headface/${senderHead}" style="display:inline;width:16px;height:16px;vertical-align:middle;margin-right:2px;" onerror="this.src='/images/headface/1.gif'">`;