Add cloud-specific missing nodes warning dialog (#6659)

## Summary
Implements a cloud-specific dialog to warn users when loading workflows
with unsupported custom nodes in Comfy Cloud. The new dialog follows the
visual style of the node conflict dialog and provides appropriate
messaging and actions.

## Changes
- Add `CloudMissingNodesHeader`, `CloudMissingNodesContent`, and
`CloudMissingNodesFooter` components
- Add `showCloudLoadWorkflowWarning` to dialogService
- Update app.ts to show cloud dialog when in cloud environment  
- Add `cloud.missingNodes` translations

## Screenshots
The dialog displays:
- Warning icon and title
- Description of the issue
- List of missing nodes
- "Learn more" link and "Ok, got it" button

## Test plan
1. Load a workflow with custom nodes in cloud environment
2. Verify cloud-specific dialog appears with appropriate styling
3. Verify "Learn more" button opens cloud documentation
4. Verify "Ok, got it" button closes dialog

## Notes
- Two unused i18n keys (`cloud.missingNodes.cannotRun` and
`cloud.missingNodes.missingNodes`) are included for future PR that will
add breadcrumb warning icons and run button disable functionality

<img width="1367" height="988" alt="스크린샷 2025-11-12 오후 4 33 38"
src="https://github.com/user-attachments/assets/75a6fced-959f-4e93-9b82-4e61b53a9ee4"
/>

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6659-Add-cloud-specific-missing-nodes-warning-dialog-2a96d73d36508161ae55fe157f55cd17)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/scripts/app.ts

@@ -1001,7 +1001,11 @@ export class ComfyApp {
 
   private showMissingNodesError(missingNodeTypes: MissingNodeType[]) {
     if (useSettingStore().get('Comfy.Workflow.ShowMissingNodesWarning')) {
-      useDialogService().showLoadWorkflowWarning({ missingNodeTypes })
+      if (isCloud) {
+        useDialogService().showCloudLoadWorkflowWarning({ missingNodeTypes })
+      } else {
+        useDialogService().showLoadWorkflowWarning({ missingNodeTypes })
+      }
     }
   }