feat: add public page fade in

src/index.css

@@ -49,6 +49,26 @@ header button {
   }
 }
 
+.ark-page-fade-in {
+  animation: ark-page-fade-in 240ms ease-out both;
+}
+
+@keyframes ark-page-fade-in {
+  from {
+    opacity: 0;
+  }
+
+  to {
+    opacity: 1;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .ark-page-fade-in {
+    animation: none;
+  }
+}
+
 /* Desktop header nav: thin scrollbar when links overflow (still 單列) */
 .header-nav-scroll {
   scrollbar-width: thin;