feat(mobile): keep search results visible (#26498)

Search results are replaced with a spinner when loading the next page,
which is quite jarring. Search results now remain visible when loading
the next page with a spinner at the bottom. The next page also loads
sooner, which makes it feel a lot smoother.

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

mobile/lib/domain/services/timeline.service.dart

@@ -78,6 +78,9 @@ class TimelineFactory {
   TimelineService fromAssets(List<BaseAsset> assets, TimelineOrigin type) =>
       TimelineService(_timelineRepository.fromAssets(assets, type));
 
+  TimelineService fromAssetStream(List<BaseAsset> Function() getAssets, Stream<int> assetCount, TimelineOrigin type) =>
+      TimelineService(_timelineRepository.fromAssetStream(getAssets, assetCount, type));
+
   TimelineService fromAssetsWithBuckets(List<BaseAsset> assets, TimelineOrigin type) =>
       TimelineService(_timelineRepository.fromAssetsWithBuckets(assets, type));
 
@@ -112,7 +115,7 @@ class TimelineService {
 
         if (totalAssets == 0) {
           _bufferOffset = 0;
-          _buffer.clear();
+          _buffer = [];
         } else {
           final int offset;
           final int count;