Library loads extremely slowly on large collections (All Albums / All Songs)

[dexsper]

Bug Description

Opening "All Albums" or "All Songs" for the first time (or after cache expires) can take several minutes on large libraries. The root cause is _refreshAllDataInBackground() in LibraryProvider, which fetches the entire library via hundreds of sequential HTTP requests:

1. getArtists() — 1 request
2. getArtistAlbums(id) — 1 request per artist, sequentially
3. getAlbumSongs(id) — 1 request per album, sequentially

On a collection of ~500 albums across ~200 artists this results in 700+ sequential API calls, blocking the screen for minutes.

Additionally, _onScroll() in AllSongsScreen is defined but empty — there is no lazy/paginated loading once the screen opens.

Steps to Reproduce

1. Fresh install or cache older than 6 hours
2. Connect to a Subsonic/Navidrome server with 200+ albums
3. Open Library → All Albums or All Songs
4. Observe loading spinner that can take 2–5+ minutes before any content appears

Expected Behavior

Albums and songs should appear quickly using paginated API calls (getAlbumList2 supports size + offset).
Content should load incrementally as the user scrolls rather than waiting for the entire library to be fetched upfront.

App Version

v1.0.8

Subsonic Server

Navidrome