feat: storage writes via storage-agent, accepts_uploads and write_template (M5.5)

- storage-agent: POST /internal/files copies a staged file into a source
  (temp file, fsync, SHA-256 check, hard link so nothing is overwritten,
  " (2)" suffix on conflict, owner PIPU_FILE_UID/GID) and
  POST /internal/files/test. NFS sources that accept uploads are mounted
  rw in an agent-only /library-rw and bind-mounted read-only for others;
  local sources are written through /library-host-rw.
- meta: write templates ({track:02}, {disc:1-}, [optional]) with name
  sanitising and length limits, suggestion from the source's regexes
  and a reversibility check against 50 catalogue tracks.
- API and admin UI: accepts_uploads / write_template on sources,
  write-template suggest and check endpoints, write test result.

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

services/api/internal/library/store.go

@@ -4,6 +4,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"path"
+	"strconv"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -41,6 +44,7 @@ type Source struct {
 	LastScanAt     *time.Time
 	CreatedAt      time.Time
 	AcceptsUploads bool
+	WriteTemplate  *string
 }
 
 // PatternRow — шаблон пути источника.
@@ -81,7 +85,8 @@ func NewStore(pool *pgxpool.Pool) *Store { return &Store{pool: pool} }
 func newID() uuid.UUID { return uuid.Must(uuid.NewV7()) }
 
 const sourceColumns = `id, name, type, nfs_server, nfs_export, nfs_options, local_path, tag_priority = 'tags_first',
-	extract(epoch from scan_interval)::bigint, status, status_message, last_scan_at, created_at, accepts_uploads`
+	extract(epoch from scan_interval)::bigint, status, status_message, last_scan_at, created_at, accepts_uploads,
+	write_template`
 
 func scanSource(row pgx.Row) (Source, error) {
 	var (
@@ -90,7 +95,7 @@ func scanSource(row pgx.Row) (Source, error) {
 		interval *int64
 	)
 	err := row.Scan(&s.ID, &s.Name, &typ, &s.NFSServer, &s.NFSExport, &s.NFSOptions, &s.LocalPath, &s.TagsFirst,
-		&interval, &s.Status, &s.StatusMessage, &s.LastScanAt, &s.CreatedAt, &s.AcceptsUploads)
+		&interval, &s.Status, &s.StatusMessage, &s.LastScanAt, &s.CreatedAt, &s.AcceptsUploads, &s.WriteTemplate)
 	if errors.Is(err, pgx.ErrNoRows) {
 		return Source{}, ErrNotFound
 	}
@@ -147,14 +152,15 @@ func tagPriority(tagsFirst bool) string {
 func (st *Store) SaveSource(ctx context.Context, s Source) (Source, error) {
 	return scanSource(st.pool.QueryRow(ctx, `
 		INSERT INTO library_sources (id, name, type, nfs_server, nfs_export, nfs_options, local_path, tag_priority,
-			scan_interval, status, status_message, created_at)
-		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, make_interval(secs => $9::bigint), $10, $11, now())
+			scan_interval, status, status_message, accepts_uploads, write_template, created_at)
+		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, make_interval(secs => $9::bigint), $10, $11, $12, $13, now())
 		ON CONFLICT (id) DO UPDATE SET name = EXCLUDED.name, nfs_server = EXCLUDED.nfs_server,
 			nfs_export = EXCLUDED.nfs_export, nfs_options = EXCLUDED.nfs_options, local_path = EXCLUDED.local_path,
-			tag_priority = EXCLUDED.tag_priority, scan_interval = EXCLUDED.scan_interval
+			tag_priority = EXCLUDED.tag_priority, scan_interval = EXCLUDED.scan_interval,
+			accepts_uploads = EXCLUDED.accepts_uploads, write_template = EXCLUDED.write_template
 		RETURNING `+sourceColumns,
 		s.ID, s.Name, string(s.Type), s.NFSServer, s.NFSExport, s.NFSOptions, s.LocalPath, tagPriority(s.TagsFirst),
-		intervalSeconds(s.ScanInterval), s.Status, s.StatusMessage))
+		intervalSeconds(s.ScanInterval), s.Status, s.StatusMessage, s.AcceptsUploads, s.WriteTemplate))
 }
 
 // SetSourceStatus обновляет состояние подключения.
@@ -683,3 +689,52 @@ func (st *Store) SaveFingerprint(ctx context.Context, fileID uuid.UUID, sum []by
 	}
 	return tx.Commit(ctx)
 }
+
+// TemplateSamples — случайные файлы источника с метаданными каталога (для проверки шаблона записи).
+func (st *Store) TemplateSamples(ctx context.Context, sourceID uuid.UUID, n int) ([]meta.TemplateSample, error) {
+	rows, err := st.pool.Query(ctx, `
+		SELECT mf.rel_path, t.title, al.title, aa.name, coalesce(t.year, al.year), t.track_no, t.disc_no,
+			coalesce((SELECT string_agg(a.name, '; ' ORDER BY ta.position) FROM track_artists ta
+				JOIN artists a ON a.id = ta.artist_id WHERE ta.track_id = t.id AND ta.role = 'main'), aa.name),
+			(SELECT max(t2.disc_no) FROM tracks t2 WHERE t2.album_id = al.id),
+			(SELECT g.name FROM track_genres tg JOIN genres g ON g.id = tg.genre_id
+				WHERE tg.track_id = t.id ORDER BY tg.weight DESC LIMIT 1)
+		FROM media_files mf
+		JOIN tracks t ON t.id = mf.track_id
+		JOIN albums al ON al.id = t.album_id
+		JOIN artists aa ON aa.id = al.album_artist_id
+		WHERE mf.source_id = $1 AND mf.missing_since IS NULL
+		ORDER BY random() LIMIT $2`, sourceID, n)
+	if err != nil {
+		return nil, fmt.Errorf("library: template samples: %w", err)
+	}
+	return pgx.CollectRows(rows, func(r pgx.CollectableRow) (meta.TemplateSample, error) {
+		var (
+			rel, title, album, albumArtist, artist string
+			year, track, disc, discs               *int
+			genre                                  *string
+		)
+		if err := r.Scan(&rel, &title, &album, &albumArtist, &year, &track, &disc, &artist, &discs, &genre); err != nil {
+			return meta.TemplateSample{}, err
+		}
+		num := func(p *int) string {
+			if p == nil || *p <= 0 {
+				return ""
+			}
+			return strconv.Itoa(*p)
+		}
+		f := meta.Fields{
+			Artist: artist, AlbumArtist: albumArtist, Album: album, Title: title, Year: num(year), Track: num(track),
+			Disc: num(disc),
+		}
+		if genre != nil {
+			f.Genre = *genre
+		}
+		count := 1
+		if discs != nil {
+			count = *discs
+		}
+		ext := strings.TrimPrefix(path.Ext(rel), ".")
+		return meta.TemplateSample{RelPath: rel, Input: meta.TemplateInput{Fields: f, DiscCount: count, Ext: ext}}, nil
+	})
+}