Whether offline library queries may include catalog items that are merely
browsed/synced but not downloaded (the greyed-out “browse the whole server”
view). Defaults to true so online browsing (which reads this same cache as
a fast path) still sees the full catalog.
Set whether offline get_items includes non-downloaded (synced-only) catalog
items. Called from the frontend: true when online or when the offline
“Show all server media” toggle is on; false when offline with the toggle
off (show downloaded/local media only).