fix: update background image handling in carbonCover for improved visual consistency

Author: medyo

src/features/adv/components/AdvBanner.css

@@ -83,20 +83,19 @@
   gap: 1em;
   font-size: 14px;
   position: relative;
-  background-image: var(--ad-dynamic-bg-image);
   transition: all 0.4s cubic-bezier(0.25, 0.46, 0.45, 0.94);
-  background-repeat: no-repeat;
-  background-size: cover;
-  background-position: center;
   --gradient-direction: 135deg;
 }
 
 .carbonCover:before {
   content: '';
   position: absolute;
   inset: 0;
+  background-image: var(--ad-dynamic-bg-image);
+  background-repeat: no-repeat;
+  background-size: cover;
+  background-position: center;
   filter: blur(10px);
-  z-index: -1;
 }
 
 .carbonCover:after {