fix(webui): label history scroll region for keyboard users

Author: 1zzxy1

dashboard/src/views/ConversationPage.vue

@@ -202,6 +202,8 @@
                         v-else
                         class="conversation-messages-container"
                         style="background-color: var(--v-theme-surface);"
+                        role="region"
+                        :aria-label="tm('history.title')"
                         tabindex="0"
                         @wheel.stop>
                         <!-- 空对话提示 -->
@@ -1113,6 +1115,11 @@ export default {
     background-color: #f9f9f9;
 }
 
+.conversation-messages-container:focus-visible {
+    outline: 2px solid rgba(var(--v-theme-primary), 0.6);
+    outline-offset: 2px;
+}
+
 /* 暗色模式下的聊天消息容器 */
 .v-theme--dark .conversation-messages-container {
     background-color: #1e1e1e;