[Feature] Improved caching on mobile app

I have searched the existing feature requests to make sure this is not a duplicate request.

• Yes

The feature

When using the immich Mobile app, there seems to be multiple possible improvements to make large photo albums for skimmable. In particular, a few features that I believe would be valuable include:

1. Option to cache low resolution thumbnails and even original assets on device
2. Viewing photo album since last connection to server (i.e. old album is visible, new photos on device since last opened is visible immediately before attempting to sync with server)

In general, it's important for the app to feel as close to photos stored on device. Could assume users has slow or no Internet in worse case and find improvements to the load speed.

Platform

• Server
• Web
• Mobile