feat(organize/scan): transfer modes, seeding-safe relocation, inode dedup, incremental scanning

- Organizer: add move/copy/hardlink/symlink transfer modes (default move),
  per-request target_path/transfer_mode overrides, and honor organize.target_dir
  / organize.transfer_mode settings.
- keep_seeding (default on): escalate move->hardlink (cross-device->copy) so the
  qBittorrent source stays in place and continues seeding after organize.
- qBittorrent SetLocation + POST /downloads/relocate to migrate whole torrents
  while keeping them seeding.
- Scanner: FileID (device:inode) hardlink dedup to avoid duplicate recognition
  and double-counted storage; extract single-file ingest.
- Watcher: recursive watch + incremental per-file ingest/remove instead of full
  re-scan; periodic full library scan now gated behind scan.periodic_enabled
  (default off) to reduce disk wear.
- Telegram bot: handle callback_query in polling, declare allowed_updates in
  webhook, answer callbacks.
- Frontend: settings for transfer mode / keep_seeding / periodic scan; organize
  panel target dir + transfer mode overrides.
- Tests for transfer modes, organizer resolution, SetLocation, inode dedup,
  incremental ingest/remove.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

internal/service/downloads.go

@@ -450,6 +450,19 @@ func (d *DownloadService) Delete(ctx context.Context, hash string, withFiles boo
 	return d.qb.Delete(ctx, hash, withFiles)
 }
 
+// RelocateTorrent moves a torrent's data to a new save directory while keeping
+// it seeding (qBittorrent performs the physical move and resumes seeding).
+// 用于「移动 PT 种子文件且转移后继续做种上传」的整盘迁移场景。
+func (d *DownloadService) RelocateTorrent(ctx context.Context, hash, location string) error {
+	if strings.TrimSpace(hash) == "" {
+		return errors.New("hash is required")
+	}
+	if strings.TrimSpace(location) == "" {
+		return errors.New("location is required")
+	}
+	return d.qb.SetLocation(ctx, hash, strings.TrimSpace(location))
+}
+
 // poll fans out qBittorrent /torrents/info every 5 s as WS events. The
 // payload is opaque to the client; the React store merges by hash.
 func (d *DownloadService) poll(ctx context.Context) {