fix: lower actividad-card background opacity to 85%, section overlay to 75%

public/index.html

@@ -319,7 +319,7 @@
       content: '';
       position: absolute;
       inset: 0;
-      background: rgba(244,244,244,0.80);
+      background: rgba(244,244,244,0.75);
     }
 
     .section-bg-actividades > * {
@@ -535,7 +535,7 @@
     }
 
     .actividad-card {
-      background: var(--color-white);
+      background: rgba(255,255,255,0.85);
       border-radius: 10px;
       overflow: hidden;
       box-shadow: 0 5px 25px rgba(0,0,0,0.08);