phsl / new-api

- Remove colorful gradient backgrounds from dashboard panel headers in Detail page
- Replace custom header styling with default Semi-UI card title styling
- Remove background images and gradient overlays from all authentication pages
- Simplify authentication page layouts with clean gray backgrounds
- Update title text colors from white to dark gray for better contrast
- Remove unnecessary z-index layering and complex positioning
- Clean up unused background image imports

This change creates a more professional and consistent visual appearance
across the application by removing distracting visual elements.