docs(plan): add M5b quarantine workflow implementation plan
16 tasks covering migration 0011, Lidarr client extensions (LookupArtistByMBID,
LookupAlbumByMBID, DeleteAlbum), library.DeleteTrackFile, lidarrquarantine.Service
(Flag/Unflag/ListMine/ListAdminQueue + Resolve/DeleteFile/DeleteViaLidarr),
soft-hide enforcement on user-context track-list reads, /api/quarantine + admin
endpoints, and frontend (TrackMenu/FlagPopover, /library/hidden, /admin/quarantine,
sidebar promotion). Mirrors the M5a plan cadence.
bvandeusen
0806a37a42