feat(api): upload queue with quota, tus intake, processing and import (M5.5)

- Migration 00008: upload_batches, upload_files, upload_quota.
- Quota reserved under a row lock when a batch is created; every status
  change goes through one transition that frees space in the same
  transaction. SHA-256 duplicates are rejected before any upload.
- tus 1.0.0 core (HEAD/PATCH) for the author only; offset is the real
  staging file size, data beyond the declared size is refused (ADR-015).
- Processing worker: ffprobe checks, SHA-256 verification, exact and
  Chromaprint duplicates against library and queue, metadata from tags
  or the dropped folder path, possible_duplicate on metadata match, and
  the target path from write_template reusing existing folder spelling.
- Import worker: edited tags written with ffmpeg stream copy, file
  written by storage-agent, point scan of the new file, imported status;
  idempotent and resumed after restart. Stale uploads expire after 24 h,
  orphan staging files are removed at startup.
- API: quota, precheck, batches, my uploads, withdraw, admin list,
  metadata edit, bulk review, retry and queue settings.

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

services/api/internal/library/store.go

@@ -244,6 +244,22 @@ func (st *Store) Files(ctx context.Context, sourceID uuid.UUID) (map[string]File
 	return out, rows.Err()
 }
 
+// FileByPath — файл источника по пути (точечный скан).
+func (st *Store) FileByPath(ctx context.Context, sourceID uuid.UUID, rel string) (FileRow, bool, error) {
+	var f FileRow
+	err := st.pool.QueryRow(ctx, `
+		SELECT id, rel_path, size_bytes, mtime, content_hash, track_id, missing_since IS NOT NULL
+		FROM media_files WHERE source_id = $1 AND rel_path = $2`, sourceID, rel).
+		Scan(&f.ID, &f.RelPath, &f.Size, &f.Mtime, &f.ContentHash, &f.TrackID, &f.Missing)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return FileRow{}, false, nil
+	}
+	if err != nil {
+		return FileRow{}, false, fmt.Errorf("library: file by path: %w", err)
+	}
+	return f, true, nil
+}
+
 // SampleFiles — случайная выборка путей источника (для предпросмотра шаблонов).
 func (st *Store) SampleFiles(ctx context.Context, sourceID uuid.UUID, n int) ([]string, error) {
 	rows, err := st.pool.Query(ctx, `