We are polishing the top-level app styling for the DevIndex application.
This task involves creating dedicated theme files for the HeaderToolbar component in both neo-dark and neo-light themes.

Scope:

• Create resources/scss/theme-neo-dark/apps/devindex/HeaderToolbar.scss
• Create resources/scss/theme-neo-light/apps/devindex/HeaderToolbar.scss
• Rename CSS variables from --portal-header-shadow to --devindex-header-shadow in resources/scss/src/apps/devindex/HeaderToolbar.scss