fix(ui): P0-4 — SaaS settings page crash from paginated API response

listRelayTasks() expected RelayTaskInfo[] but API returns
{items:[], total:0, page:1, page_size:20}. When setTasks() received
the paginated object, tasks.map() crashed during render, triggering
the ErrorBoundary fallback "SaaS 平台加载失败".

Fix: extract .items from paginated response with Array.isArray fallback.
Also adds onError logging to ErrorBoundary wrappers for easier debugging.

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

desktop/src/components/Settings/SettingsLayout.tsx

@@ -113,6 +113,9 @@ export function SettingsLayout({ onBack }: SettingsLayoutProps) {
       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>}
+          onError={(err, info) => {
+            console.error('[Settings] SaaS page render error:', err, info.componentStack);
+          }}
         >
           <SaaSSettings />
         </ErrorBoundary>
@@ -120,6 +123,9 @@ export function SettingsLayout({ onBack }: SettingsLayoutProps) {
       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>}
+          onError={(err, info) => {
+            console.error('[Settings] Billing page render error:', err, info.componentStack);
+          }}
         >
           <PricingPage />
         </ErrorBoundary>