feat(app): update scroll-to-top button colors for improved visibility

src/client/dd-hub-react/src/app.tsx

@@ -48,14 +48,14 @@ export default function App({ children }: AppProps) {
         height: 48,
         position: 'fixed',
         color: 'common.white',
-        bgcolor: 'primary.main',
+        bgcolor: '#a52431',
         boxShadow: (theme) => theme.shadows[6],
         opacity: showScrollTop ? 1 : 0,
         pointerEvents: showScrollTop ? 'auto' : 'none',
         transform: showScrollTop ? 'translateY(0)' : 'translateY(12px)',
         transition: 'opacity 0.24s ease, transform 0.24s ease',
         '&:hover': {
-          bgcolor: 'primary.dark',
+          bgcolor: '#8c1e2a',
           boxShadow: (theme) => theme.shadows[8],
         },
       }}