fix(web): viewport reactivity, off-screen thumbhashes being rendered (#15435)

* viewport optimizations

* fade in

* async bitmap

* fast path for smaller date groups

---------

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

web/src/lib/stores/assets.store.ts

@@ -232,6 +232,7 @@ export class AssetStore {
   albumAssets: Set<string> = new Set();
   pendingScrollBucket: AssetBucket | undefined;
   pendingScrollAssetId: string | undefined;
+  maxBucketAssets = 0;
 
   listeners: BucketListener[] = [];
 
@@ -560,6 +561,7 @@ export class AssetStore {
 
       bucket.assets = assets;
       bucket.dateGroups = splitBucketIntoDateGroups(bucket, get(locale));
+      this.maxBucketAssets = Math.max(this.maxBucketAssets, assets.length);
       this.updateGeometry(bucket, true);
       this.timelineHeight = this.buckets.reduce((accumulator, b) => accumulator + b.bucketHeight, 0);
       bucket.loaded();