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/acquire/memory.go

@@ -21,6 +21,9 @@ const (
 	BlockFiles    = "files"
 	// BlockImport: the import found its files were not the album (#5522).
 	BlockImport = "import"
+	// BlockStalled: given up on because it would not finish (#5523); held
+	// back until the block's expires_at.
+	BlockStalled = "stalled"
 )
 
 // Grab origins, matching grabs_origin_check.
@@ -92,11 +95,22 @@ func (m *Memory) blocked(ctx context.Context) map[string]string {
 
 // BlockSentence is what a blocked candidate says.
 func BlockSentence(reason, detail string) string {
-	if reason == BlockFiles {
+	switch reason {
+	case BlockFiles:
 		if detail != "" {
 			return "Set aside for what its files hold: " + detail
 		}
 		return "Set aside for what its files hold."
+	case BlockImport:
+		if detail != "" {
+			return "Refused on import: " + detail
+		}
+		return "Refused on import: its files were not the album."
+	case BlockStalled:
+		if detail != "" {
+			return "Given up on for now: " + detail
+		}
+		return "Given up on for now: it would not finish."
 	}
 	return "You set this release aside."
 }

internal/acquire/settings.go

@@ -12,8 +12,11 @@ package acquire
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"time"
 
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
@@ -154,6 +157,19 @@ func DownloadClient(row dbq.AcquisitionService) (downloader.Driver, error) {
 	return downloader.Mapped(d, downloader.PathMap{Local: row.LocalPath, Remote: row.RemotePath}), nil
 }
 
+// DownloadClientFor builds the download client a grab went to, by the code
+// of its acquisition_services row.
+func DownloadClientFor(ctx context.Context, pool *pgxpool.Pool, code string) (downloader.Driver, error) {
+	row, err := dbq.New(pool).GetAcquisitionService(ctx, code)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, fmt.Errorf("the download client %q is no longer set up", code)
+		}
+		return nil, err
+	}
+	return DownloadClient(row)
+}
+
 // Sources builds every enabled search source.
 func Sources(ctx context.Context, pool *pgxpool.Pool) ([]Source, error) {
 	rows, err := dbq.New(pool).ListUsableAcquisitionServices(ctx, JobSearch)