* 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
* Fixed app not resuming backup after closing and reopening the app
* Fixed cosmetic effect of backup button doesn't change state right away after pressing start backup
* Fixed grammar
* Fixed deep copy problem that cause incorrect asset count when backing up
* Format code
* Update photo_manager pub package
* Added download endpoint for assets
* Successfully save a photo to the local device's gallery
* Save save a video to the local device's gallery
* Fixed#97
* Added download loading indicator
* Refactor and increase the font size for curated search thumbnail images
* Reposition loading animation on the search result page
