Go back to the hardlink deduplicator (1da0132), keeping backups

Restores the code of 1da0132 ("Add a setting to hide the quarantine from
Plex") and removes everything added after it: the tag editor, album art,
organizing/naming, the step-by-step tune-up and library types.

Kept:
- Database backups (Settings -> Backups): scheduled, manual, download,
  restore, and the optional backup before every action.
- The .env-driven docker-compose.yml for Arcane.

Databases that already ran the later migrations keep working: migrations
6-10 stay in the list (they only add columns) so numbering never goes
backwards, and Undo refuses History entries of removed features instead
of treating them as links.

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

internal/engine/engine.go

@@ -13,12 +13,9 @@ import (
 	"sync"
 	"time"
 
-	"github.com/cdnutter/playlink/internal/art"
 	"github.com/cdnutter/playlink/internal/fsops"
-	"github.com/cdnutter/playlink/internal/meta"
 	"github.com/cdnutter/playlink/internal/probe"
 	"github.com/cdnutter/playlink/internal/store"
-	"github.com/cdnutter/playlink/internal/tags"
 )
 
 // DefaultExtensions are the audio file types considered by default.
@@ -44,20 +41,7 @@ type Engine struct {
 	// the same files.
 	mu sync.Mutex
 
-	tagTools     tags.Tools
 	beforeAction func(ctx context.Context, reason string) error
-	tagCache     tagCache
-	artClient    *art.Client
-	artStore     *art.Store
-
-	meta *meta.Client
-
-	fixMu    sync.Mutex
-	fixPlans map[int64]*FixPlan // latest fixer check per pair
-	fixSeq   int64
-
-	plansMu sync.Mutex
-	plans   map[int64]*organizePlan // latest "rename now" preview per pair
 
 	jobsMu sync.Mutex
 	jobs   map[int64]*Job
@@ -84,7 +68,6 @@ type Job struct {
 	Error      string         `json:"error"`
 	Results    map[string]int `json:"results"`
 	Skipped    []string       `json:"skipped"`
-	Notes      []string       `json:"notes"`
 	StartedAt  int64          `json:"started_at"`
 	FinishedAt int64          `json:"finished_at,omitempty"`
 
@@ -106,15 +89,6 @@ func (j *Job) tick() { j.update(func(j *Job) { j.Done++ }) }
 
 func (j *Job) count(key string) { j.update(func(j *Job) { j.Results[key]++ }) }
 
-// note records an informational line (e.g. which cover was chosen).
-func (j *Job) note(msg string) {
-	j.update(func(j *Job) {
-		if len(j.Notes) < 300 {
-			j.Notes = append(j.Notes, msg)
-		}
-	})
-}
-
 func (j *Job) skip(msg string) {
 	j.update(func(j *Job) {
 		j.Results["skipped"]++
@@ -138,7 +112,6 @@ func (e *Engine) Job(pairID int64) *Job {
 		cp.Results[k] = v
 	}
 	cp.Skipped = append([]string{}, j.Skipped...) // never nil: the UI expects an array
-	cp.Notes = append([]string{}, j.Notes...)
 	return &cp
 }
 
@@ -316,16 +289,6 @@ func (e *Engine) NormalizePair(p *store.Pair) ([]store.Warning, error) {
 	if p.RetentionDays < 0 || p.ScanIntervalMinutes < 0 || p.SettleMinutes < 0 {
 		return nil, errors.New("intervals must not be negative")
 	}
-	switch p.LibraryType {
-	case "":
-		p.LibraryType = LibraryMusic
-	case LibraryMusic, LibrarySoundtracks:
-	default:
-		return nil, errors.New("library type must be music or soundtracks")
-	}
-	if err := normalizeOrganize(p); err != nil {
-		return nil, err
-	}
 	if p.ApproxThreshold == 0 {
 		p.ApproxThreshold = 85
 	}