Add organizing files into Artist/Album/01 Title from their tags

A new Organize tab renames audio files from their tags into a per-pair
naming pattern, by default {artist}/{album}/{track} {title} (album
artist, falling back to artist). Multi-disc albums get a disc prefix
(2-04) or a Disc N folder; names are made safe for Windows/SMB shares.

- Preview first: every rename, files already organized, and files
  skipped with the reason (missing tags, with a button into the tag
  editor; two files resolving to the same name; an existing file).
- Applying re-checks each file against the preview, moves it within its
  library (hardlinks and contents untouched, case-only renames via a
  temporary name, completed on startup after a crash), carries .lrc
  lyrics and folder cover art along, and removes emptied folders. Each
  move is an operation that can be undone; the library is rescanned.
- Optional automatic organizing of the slave, master or both during
  scans (off by default). Dry run applies.
- Scans now recognise a slave file that is a hardlink of a master file
  at a different path as linked ("same file, other path") instead of
  unmatched.

Migration 7 adds the per-pair naming settings.

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

internal/engine/scan.go

@@ -287,6 +287,11 @@ func (e *Engine) scan(ctx context.Context, j *Job, pairID int64, trigger string)
 		_ = e.st.FinishScan(ctx, pairID, started.Unix(), err.Error(), nil)
 		return err
 	}
+	if l.pair.AutoOrganize != "" && l.pair.AutoOrganize != "off" {
+		if err := e.autoOrganize(ctx, j, l); err != nil {
+			e.log.Warn("auto-organize failed", "pair", l.pair.Name, "err", err)
+		}
+	}
 	warns := layoutWarnings(l)
 
 	j.phase("Indexing master library", 0)
@@ -304,6 +309,15 @@ func (e *Engine) scan(ctx context.Context, j *Job, pairID int64, trigger string)
 		return err
 	}
 	ix := buildIndex(masterFiles, l.pair)
+	// The same file (hardlink) can sit at another path, e.g. after one library
+	// was organized; it is recognised as linked rather than unmatched.
+	byInode := map[[2]uint64]string{}
+	for _, rel := range sortedKeys(masterFiles) {
+		in := masterFiles[rel]
+		if _, dup := byInode[[2]uint64{in.Dev, in.Ino}]; !dup {
+			byInode[[2]uint64{in.Dev, in.Ino}] = rel
+		}
+	}
 	if ix.approx != nil {
 		ix.verify = e.artistVerifier(ctx, l)
 	}
@@ -322,6 +336,11 @@ func (e *Engine) scan(ctx context.Context, j *Job, pairID int64, trigger string)
 		si := slaveFiles[rel]
 		m := store.Match{PairID: pairID, RelSlave: rel}
 		m.RelMaster, m.Kind, m.Reason = ix.find(rel)
+		if m.Kind != store.KindPath {
+			if mrel, ok := byInode[[2]uint64{si.Dev, si.Ino}]; ok {
+				m.RelMaster, m.Kind, m.Reason = mrel, store.KindInode, ""
+			}
+		}
 		var pm *store.Match
 		if p, ok := prev[rel]; ok {
 			pm = &p