feat(image-modal): enhance gesture handling and improve pinch zoom functionality

src/app/shared/components/image-modal/image-modal.component.html

@@ -1,8 +1,8 @@
 <div
   class="image-modal"
+  [class.image-modal--gesturing]="gestureActive()"
   [class.image-modal--settling]="swipeSettling()"
   [style.transform]="swipeTransform()"
-  [style.opacity]="swipeOpacity()"
 >
   <div
     #viewport
@@ -22,6 +22,7 @@
         [src]="data.src"
         [alt]="data.alt"
         [style.transform]="transform()"
+        decoding="async"
         draggable="false"
         (load)="onImageLoad()"
         (error)="imageFailed.set(true)"