- Added link_overlay_enabled, link_overlay_color, link_overlay_opacity to DesignSettings model
- Created migration 0008 for new fields
- Updated CustomizationPanel with link overlay controls section
- Added validation for new overlay settings in serializer
- Updated PublicDesignSettingsSerializer to include overlay settings
- Applied link overlay to all ExpandableGroup components in public page
- Added preview in customization panel for link overlay effect
