Reset button background and border styles in styles.css

- Ensure <button class="btn"> elements default to transparent backgrounds
- Ensure .btn-outline uses transparent background to avoid browser-default user-agent button styling
- Set border: none on .btn-primary

styles.css

@@ -467,10 +467,16 @@
     transform: translateY(-1px);
   }
 
+  button.btn {
+    cursor: pointer;
+    background: transparent;
+  }
+
   .btn-primary {
     background: linear-gradient(180deg, var(--gold-bright), var(--gold));
     color: var(--ground-2);
     font-weight: 500;
+    border: none;
   }
 
   .btn-primary:hover {
@@ -480,6 +486,7 @@
   .btn-outline {
     border: 1px solid var(--gold-dim);
     color: var(--gold-bright);
+    background: transparent;
   }
 
   /* .nav-cta mirrors this hover treatment */