[2.4] Unable to create CMS pages with the same URL key for different channels

Describe the bug When managing multiple channels in Bagisto, merchants need to create channel-specific CMS pages (e.g., "About Us") with identical, SEO-friendly paths like page/about-us. Currently, the system prevents this by throwing the error "The url key has already been taken."

To Reproduce Steps to reproduce the behavior:

1. Go to 'Settings->Channels->create channel,Admin->CMS->create cms'
2. Create a new page for Channel A with the URL key about-us. Save it.
3. Create another page for Channel B and enter the same URL key about-us.
4. Try to save the page.

Expected behavior The system should allow using the same URL key for different pages as long as they are assigned to different channels.