## Summary
Adds a dedicated upgrade modal that appears when users without private
models access try to upload models, providing a clear path to upgrade
their subscription.
## Changes
- **New upgrade modal**: Created `UploadModelUpgradeModal` with
dedicated body, header, and footer components
- **Conditional rendering**: Modified `AssetBrowserModal` to show
upgrade modal when `privateModelsEnabled` flag is false
- **Subscription integration**: Connected upgrade flow to existing
subscription system via `showSubscriptionDialog()`
- **Localization**: Added localization keys for upgrade messaging
## Review Focus
- Conditional logic in `AssetBrowserModal.handleUploadClick()` based on
feature flags
- Component naming consistency (all upgrade-related components prefixed
with `UploadModelUpgrade`)
- Footer component refactoring maintains existing upload wizard behavior
🤖 Generated with [Claude Code](https://claude.com/claude-code)
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7124-feat-add-upgrade-modal-for-model-upload-when-private-models-disabled-2be6d73d36508147b72eea8a1d6ab772)
by [Unito](https://www.unito.io)
---------
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>
