fix(web): use correct sliding window offset for search results (#20726)

The contents of search results are slightly offset by the search bar, search
terms and spacing (margins/padding), and needs to be factored in when
calculating whether an asset is visible or not. The offset was 0, which
meant that assets were removed from view too early.

Author: uhthomas

web/src/routes/(user)/search/[[photos=photos]]/[[assetId=id]]/+page.svelte

@@ -52,6 +52,7 @@
 
   let { isViewing: showAssetViewer } = assetViewingStore;
   const viewport: Viewport = $state({ width: 0, height: 0 });
+  let searchResultsElement: HTMLElement | undefined = $state();
 
   // The GalleryViewer pushes it's own history state, which causes weird
   // behavior for history.back(). To prevent that we store the previous page
@@ -362,6 +363,7 @@
   class="mb-12 bg-immich-bg dark:bg-immich-dark-bg m-4"
   bind:clientHeight={viewport.height}
   bind:clientWidth={viewport.width}
+  bind:this={searchResultsElement}
 >
   {#if searchResultAlbums.length > 0}
     <section>
@@ -381,8 +383,8 @@
         onIntersected={loadNextPage}
         showArchiveIcon={true}
         {viewport}
-        pageHeaderOffset={54}
         onReload={onSearchQueryUpdate}
+        slidingWindowOffset={searchResultsElement.offsetTop}
       />
     {:else if !isLoading}
       <div class="flex min-h-[calc(66vh-11rem)] w-full place-content-center items-center dark:text-white">