The cache management page walked and deleted directories itself. Move
_scanDirectory and _clearDirectoryContents verbatim into
CacheMaintenanceService.scanDirectory and clearDirectoryContents in
lib/services/cache_maintenance_service.dart, with _DirectoryStats
becoming the public DirectoryStats it returns.
The page calls the service at the same points with the same arguments,
so scan concurrency, the 24-entity delete chunks, the directory
re-creation after clearing and every action key are unchanged.
zarzet
8fffb9230a