feat: download lifecycle — stalled and failed downloads are given up and searched again; imported ones seed, then go (M502 #5523)

Ported from Fabled Librarian's System 104. A new lifecycle poller, every
ten minutes:
- a download the client fails is given up at once;
- one nobody shares, or still fetching its file list, past the stall
  setting (6 h) is asked for again three times, then given up;
- giving up removes the download with its files, holds the release back
  for a week (release_blocks.expires_at), ends the grab and searches the
  album again, with no limit per album;
- a running download the client stops listing for half an hour ends and is
  searched again, not held back; an empty list is not taken as gone;
- an imported download seeds to ratio 2.0 or 14 days, then is removed;
- a download the client would not remove is asked again every pass.

Every condition and act is one open row per (client, download, condition)
in download_interventions. Activity shows what is wrong with a download and
how often it was retried, why one ended, its seeding, and a banner for a
client that does not answer. A running download can be given up by hand
(set aside for good). The seed ratio, seed days and stall hours are on the
search settings card. The download client lookup moves to
acquire.DownloadClientFor, shared by the importer and the lifecycle.

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

internal/db/queries/wanted.sql

@@ -194,7 +194,7 @@ SELECT w.id, w.release_group_mbid, w.artist_mbid, w.artist_name, w.title, w.reas
        gr.id AS grab_id, gr.name AS grab_name, gr.grabbed_at, gr.origin AS grab_origin,
        gr.quality AS grab_quality, gr.ended_at AS grab_ended_at, gr.end_reason AS grab_end_reason,
        gr.progress AS grab_progress, gr.import_state AS grab_import_state,
-       gr.import_reason AS grab_import_reason, gr.imported_at AS grab_imported_at,
+       gr.import_reason AS grab_import_reason, gr.end_detail AS grab_end_detail, gr.imported_at AS grab_imported_at,
        gr.imported_files AS grab_imported_files
   FROM wants w
   LEFT JOIN users u ON u.id = w.created_by
@@ -219,5 +219,6 @@ SELECT COUNT(*) FILTER (WHERE fulfilled_at IS NULL AND reason <> 'missing')::big
        (SELECT COUNT(*) FROM grabs WHERE ended_at IS NULL)::bigint                  AS activity,
        (SELECT COUNT(*) FROM grabs
          WHERE ended_at IS NULL AND import_state IN ('review', 'failed'))::bigint   AS attention,
-       (SELECT COUNT(*) FROM release_blocks)::bigint                                AS blocked
+       (SELECT COUNT(*) FROM release_blocks b
+         WHERE b.expires_at IS NULL OR b.expires_at > now())::bigint               AS blocked
   FROM wants;