fix(desktop): 功能验证 6 项缺陷修复

- ISS-002: SkillInfoResponse 增加 source/path 字段，修复技能系统显示 0 个
- ISS-003: Sidebar 添加自动化/技能市场导航入口 + App 返回按钮
- ISS-004: SaaS fetchAvailableModels 添加 .catch() 防限流崩溃
- ISS-006: SaaSSettings/PricingPage 包裹 ErrorBoundary 防白屏
- ISS-008: listModels 加载 localStorage 自定义模型，修复仅显示 1 个模型
- configStore listSkills 映射添加 source/path 转发

desktop/src/components/Settings/SettingsLayout.tsx

@@ -41,6 +41,7 @@ import { SecureStorage } from './SecureStorage';
 import { VikingPanel } from '../VikingPanel';
 import { SaaSSettings } from '../SaaS/SaaSSettings';
 import { PricingPage } from '../SaaS/PricingPage';
+import { ErrorBoundary } from '../ui/ErrorBoundary';
 
 interface SettingsLayoutProps {
   onBack: () => void;
@@ -105,8 +106,20 @@ export function SettingsLayout({ onBack }: SettingsLayoutProps) {
       case 'workspace': return <Workspace />;
       case 'privacy': return <Privacy />;
       case 'storage': return <SecureStorage />;
-      case 'saas': return <SaaSSettings />;
-      case 'billing': return <PricingPage />;
+      case 'saas': return (
+        <ErrorBoundary
+          fallback={<div className="p-6 text-center text-gray-500">SaaS 平台加载失败，请稍后重试</div>}
+        >
+          <SaaSSettings />
+        </ErrorBoundary>
+      );
+      case 'billing': return (
+        <ErrorBoundary
+          fallback={<div className="p-6 text-center text-gray-500">计费信息加载失败，请稍后重试</div>}
+        >
+          <PricingPage />
+        </ErrorBoundary>
+      );
       case 'security': return (
         <div className="space-y-6">
           <div>