fix: resolve toast message visibility and deployment success notifications

## Issues Fixed
- Toast messages appearing in background/blurred due to z-index conflicts
- Missing success toast notifications for deployment completions
- Scoped ToastContainer limiting toast visibility to chat component only

## Changes Made

### Global Toast System
- Move ToastContainer from Chat.client.tsx to root.tsx for global availability
- Add highest z-index (1000) to ensure toasts appear above all UI elements
- Remove duplicate ToastContainer from chat component

### Z-Index System Updates
- Add .z-toast class with z-index: $zIndexMax + 1 (1000)
- Apply toast z-index to .Toastify__toast-container in toast.scss
- Ensure proper layering hierarchy for all toast messages

### Deployment Success Notifications
- Add missing toast.success() calls to all deployment services:
  - NetlifyDeploy: "🚀 Netlify deployment completed successfully!"
  - VercelDeploy: "🚀 Vercel deployment completed successfully!"
  - GitHubDeploy: "🚀 GitHub deployment preparation completed successfully!"
  - GitLabDeploy: "🚀 GitLab deployment preparation completed successfully!"

## Result
- All toast messages now appear in foreground with proper z-index
- Deployment success notifications are clearly visible to users
- Consistent toast behavior across the entire application
- No more blurred or background toast messages

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

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

app/components/deploy/VercelDeploy.client.tsx

@@ -213,6 +213,9 @@ export function useVercelDeploy() {
         source: 'vercel',
       });
 
+      // Show success toast notification
+      toast.success(`🚀 Vercel deployment completed successfully!`);
+
       return true;
     } catch (err) {
       console.error('Vercel deploy error:', err);