Remove button shine/sweep hover effect

- Remove .btn::before pseudo-element that created moving white box on hover

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

index.html

@@ -297,20 +297,6 @@
             overflow: hidden;
         }
 
-        .btn::before {
-            content: '';
-            position: absolute;
-            top: 0;
-            left: -100%;
-            width: 100%;
-            height: 100%;
-            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
-            transition: left 0.5s;
-        }
-
-        .btn:hover::before {
-            left: 100%;
-        }
 
         .btn-primary {
             background: var(--gradient-1);