refactor(mobile): reworked Asset, store all required fields from local & remote (#1539)

replace usage of AssetResponseDto with Asset

Add new class ExifInfo to store data from ExifResponseDto

mobile/lib/shared/services/json_cache.dart

@@ -60,5 +60,5 @@ abstract class JsonCache<T> {
   }
 
   void put(T data);
-  Future<T> get();
+  Future<T?> get();
 }