feat(mobile): show local assets (#905)

* introduce Asset as composition of AssetResponseDTO and AssetEntity

* filter out duplicate assets (that are both local and remote, take only remote for now)

* only allow remote images to be added to albums

* introduce ImmichImage to render Asset using local or remote data

* optimized deletion of local assets

* local video file playback

* allow multiple methods to wait on background service finished

* skip local assets when adding to album from home screen

* fix and optimize delete

* show gray box placeholder for local assets

* add comments

* fix bug: duplicate assets in state after onNewAssetUploaded

mobile/lib/modules/backup/models/hive_backup_albums.model.dart

@@ -46,6 +46,17 @@ class HiveBackupAlbums {
     );
   }
 
+  /// Returns a deep copy to allow safe modification without changing the global
+  /// state of [HiveBackupAlbums] before actually saving the changes
+  HiveBackupAlbums deepCopy() {
+    return HiveBackupAlbums(
+      selectedAlbumIds: selectedAlbumIds.toList(),
+      excludedAlbumsIds: excludedAlbumsIds.toList(),
+      lastSelectedBackupTime: lastSelectedBackupTime.toList(),
+      lastExcludedBackupTime: lastExcludedBackupTime.toList(),
+    );
+  }
+
   Map<String, dynamic> toMap() {
     final result = <String, dynamic>{};