[feat] Add cloud notification modal for macOS desktop users

Adds a one-time informational modal that introduces Comfy Cloud to macOS desktop users. The modal emphasizes that ComfyUI remains free and open source, with Cloud as an optional service for GPU access.

Key features:
- Shows once on first launch for macOS + Electron users
- Persistent badge in topbar after dismissal for easy re-access
- Clean design with Comfy Cloud branding
- Non-intrusive messaging focused on infrastructure benefits

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

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

src/schemas/apiSchema.ts

@@ -374,6 +374,7 @@ const zSettings = z.object({
   'Comfy.Workflow.ShowMissingNodesWarning': z.boolean(),
   'Comfy.Workflow.ShowMissingModelsWarning': z.boolean(),
   'Comfy.Workflow.WarnBlueprintOverwrite': z.boolean(),
+  'Comfy.Desktop.CloudNotificationShown': z.boolean(),
   'Comfy.DisableFloatRounding': z.boolean(),
   'Comfy.DisableSliders': z.boolean(),
   'Comfy.DOMClippingEnabled': z.boolean(),