update_available only compared the latest Gitea release against what's
staged, not what the frame is actually running -- so once a release
was staged (manually or via auto-update) but the frame hadn't woken up
and applied it yet, "Check now" reported "Up to date" even though the
device was still on the old version. Report the frame's actual running
version and use it to show a distinct "staged, applies on next wake"
message instead.
