feat(cloud): add asset widget support for PrimitiveNode model selection (#8598)

Add cloud asset widget creation in `_createWidget()` using
`isAssetBrowserEligible()`
- Extract shared `createAssetWidget` factory to
`src/platform/assets/utils/`
- Refactor `useComboWidget.ts` to use the shared factory
- Add `_finalizeWidget()` helper to DRY up widget sizing/callback setup
- Pass target node's `comfyClass` and input name to Asset Browser for
correct model filtering
- Check `Comfy.Assets.UseAssetAPI` setting (matches `useComboWidget.ts`
behavior)
- Sync existing target widget value to asset widget
- Add toast notifications for asset validation errors
- Add i18n translations for invalidAsset and invalidFilename errors

Supersedes #8461 (clean rebase, no merge commits)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8598-feat-cloud-add-asset-widget-support-for-PrimitiveNode-model-selection-2fd6d73d365081a8afa7c2e91762f11c)
by [Unito](https://www.unito.io)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced asset widget integration for cloud-based model selection,
enabling users to browse and select assets through an improved
interface.
* Added comprehensive asset validation with enhanced error messages for
invalid assets and filenames.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

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src/locales/en/main.json

@@ -2633,6 +2633,10 @@
     "errorUploadFailed": "Failed to import asset. Please try again.",
     "errorUserTokenAccessDenied": "Your API token does not have access to this resource. Please check your token permissions.",
     "errorUserTokenInvalid": "Your stored API token is invalid or expired. Please update your token in settings.",
+    "invalidAsset": "Invalid Asset",
+    "invalidAssetDetail": "The selected asset could not be validated. Please try again.",
+    "invalidFilename": "Invalid Filename",
+    "invalidFilenameDetail": "The asset filename could not be determined. Please try again.",
     "failedToCreateNode": "Failed to create node. Please try again or check console for details.",
     "fileFormats": "File formats",
     "fileName": "File Name",