feat(mobile): inline asset details (#25952)

The existing implementation for showing asset details uses a bottom
sheet, and is not in sync with the preview or scroll intent. Other apps
use inline details, which is much cleaner and feels better to use.

mobile/lib/presentation/widgets/asset_viewer/asset_preloader.dart

@@ -0,0 +1,46 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:immich_mobile/domain/models/asset/base_asset.model.dart';
+import 'package:immich_mobile/domain/services/timeline.service.dart';
+import 'package:immich_mobile/presentation/widgets/images/image_provider.dart';
+
+class AssetPreloader {
+  static final _dummyListener = ImageStreamListener((image, _) => image.dispose());
+
+  final TimelineService timelineService;
+  final bool Function() mounted;
+
+  Timer? _timer;
+  ImageStream? _prevStream;
+  ImageStream? _nextStream;
+
+  AssetPreloader({required this.timelineService, required this.mounted});
+
+  void preload(int index, Size size) {
+    unawaited(timelineService.preloadAssets(index));
+    _timer?.cancel();
+    _timer = Timer(Durations.medium4, () async {
+      if (!mounted()) return;
+      final (prev, next) = await (
+        timelineService.getAssetAsync(index - 1),
+        timelineService.getAssetAsync(index + 1),
+      ).wait;
+      if (!mounted()) return;
+      _prevStream?.removeListener(_dummyListener);
+      _nextStream?.removeListener(_dummyListener);
+      _prevStream = prev != null ? _resolveImage(prev, size) : null;
+      _nextStream = next != null ? _resolveImage(next, size) : null;
+    });
+  }
+
+  ImageStream _resolveImage(BaseAsset asset, Size size) {
+    return getFullImageProvider(asset, size: size).resolve(ImageConfiguration.empty)..addListener(_dummyListener);
+  }
+
+  void dispose() {
+    _timer?.cancel();
+    _prevStream?.removeListener(_dummyListener);
+    _nextStream?.removeListener(_dummyListener);
+  }
+}