Wire the per-history-entry scroll memory (added for Local Library) into
every top-level view: Home/Discover, Album, Local Album, Artist, Musician,
Label, Label Releases, Location, Favorites, Mix, Playlist, Playlist Manager,
Offline Manager, Search, Settings.
Each view's primary scroll container reports its viewport-y and restores it
on back/forward via NavState.restore-scope (scope_for in main.rs maps each
entry to a stable id; tab views carry the tab, e.g. "fav:albums"). The
container restores once per arm, only after content lays out, then clears
the scope. A `changed sr-armed` trigger covers views that persist across
sub-tab navigation (Home's Discover tabs, Favorites' shared list, Playlist
A->B->A) where no fresh mount occurs.
ScrollView-based views (Offline Manager, Settings) use visible-height for
the overflow check; ListView/Flickable views use height. Favorites' shared
albums/artists/playlists/labels Flickable matches the active tab's scope
dynamically.
cc
vicrodh
46673b2077