fix(desktop): 修复 10 个 agent 对话测试发现的缺陷

- BUG-001+002 P0: 模型选择器合并 SaaS 可用模型列表
- BUG-003 P1: 修复 relay 错误消息重复显示
- BUG-005 P1: 设置页面显示实际连接模式和地址
- BUG-006 P2: 统一 UI 语言为中文
- BUG-009 P3: 错误时隐藏建议按钮
- BUG-010 P3: 密码切换按钮添加 aria-label

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/components/ui/EmptyState.tsx

@@ -100,8 +100,8 @@ export function EmptyConversations({ action, className, size }: PrebuiltEmptySta
   return (
     <EmptyState
       icon={<Inbox className="w-8 h-8" />}
-      title="No conversations"
-      description="Your conversation history will appear here."
+      title="暂无对话"
+      description="你的对话历史将显示在这里。"
       action={action}
       className={className}
       size={size}
@@ -177,8 +177,8 @@ export function EmptyAgents({ action, className, size }: PrebuiltEmptyStateProps
  * Empty state for welcome screen.
  */
 export function WelcomeEmptyState({
-  title = "Welcome to ZCLAW",
-  description = "Send a message to start the conversation.",
+  title = "欢迎使用 ZCLAW",
+  description = "发送消息开始对话。",
   connected = true,
   action,
   className,