Signed in, Export Library wrote only the local library, and because My
Library's workspace is the cloud one then, it also dropped every local
folder and the strategies in them. Exporting a cloud folder did nothing.

Export Library now walks the local library from disk and, signed in, the
user's own cloud folders and strategies beside it, each strategy written
from the server's full copy with its images. Folder export reads the
folder from the store its card belongs to. When the cloud can't be read,
an image can't be downloaded, or this device's changes haven't synced,
the export stops and says so on screen instead of writing a backup that
leaves work out.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>