feat: enhance PhotoswipeReader with loading states for images and add fade-in animation for improved user experience

src/styles/globals.css

@@ -116,4 +116,18 @@ body {
     backdrop-filter: blur(16px);
     -webkit-backdrop-filter: blur(16px);
   }
+
+  /* Fade-in animation */
+  @keyframes fade-in {
+    from {
+      opacity: 0;
+    }
+    to {
+      opacity: 1;
+    }
+  }
+
+  .animate-fade-in {
+    animation: fade-in 0.3s ease-in forwards;
+  }
 }