feat: add error handling and timeout recovery to cloud onboarding (#5573)

Implements robust error handling and authentication timeout recovery for the cloud onboarding flow:

- Enhanced UserCheckView with VueUse useAsyncState for declarative error handling
- Added parallel API calls for better performance using Promise.all
- Implemented loading states with skeleton views and user-friendly error messages
- Added authentication timeout handling (16s) with recovery options
- Created CloudAuthTimeoutView with "Sign Out & Try Again" functionality
- Added comprehensive i18n support for error states

src/locales/en/main.json

@@ -1806,6 +1806,14 @@
       "learnAboutButton": "Learn about Cloud",
       "wantToRun": "Want to run comfyUI locally instead?",
       "download": "Download ComfyUI"
+    },
+    "checkingStatus": "Checking your account status...",
+    "retrying": "Retrying...",
+    "retry": "Try Again",
+    "authTimeout": {
+      "title": "Connection Taking Too Long",
+      "message": "We're having trouble connecting to ComfyUI Cloud. This could be due to a slow connection or temporary service issue.",
+      "restart": "Sign Out & Try Again"
     }
   }
 }