feat: adaptive progressive image loading for photo viewer (#26636)

* feat(web): adaptive progressive image loading for photo viewer

Replace ImageManager with a new AdaptiveImageLoader that progressively
loads images through quality tiers (thumbnail → preview → original).

New components and utilities:
- AdaptiveImage: layered image renderer with thumbhash, thumbnail,
  preview, and original layers with visibility managed by load state
- AdaptiveImageLoader: state machine driving the quality progression
  with per-quality callbacks and error handling
- ImageLayer/Image: low-level image elements with load/error lifecycle
- PreloadManager: preloads adjacent assets for instant navigation
- AlphaBackground/DelayedLoadingSpinner: loading state UI

Zoom is handled via a derived CSS transform applied to the content
wrapper in AdaptiveImage, with the zoom library (zoomTarget: null)
only tracking state without manipulating the DOM directly.

Also adds scaleToCover to container-utils and getAssetUrls to utils.

* fix: don't partially render images in firefox

* add passive loading indicator to asset-viewer

---------

Co-authored-by: Alex <alex.tran1502@gmail.com>

web/src/lib/components/DelayedLoadingSpinner.svelte

@@ -0,0 +1,20 @@
+<script lang="ts">
+  import { LoadingSpinner } from '@immich/ui';
+</script>
+
+<div class="delayed-spinner absolute flex h-full items-center justify-center">
+  <LoadingSpinner />
+</div>
+
+<style>
+  @keyframes delayedVisibility {
+    to {
+      visibility: visible;
+    }
+  }
+
+  .delayed-spinner {
+    visibility: hidden;
+    animation: 0s linear 0.4s forwards delayedVisibility;
+  }
+</style>