Fix Jellyfin playlist integration and tracklist matching for single-CD albums

- hint_extractor: add _normalize_vertical_tracklist() to handle bare-number/
  title/duration format (Tufaranka-style tracklists)
- hint_extractor: fix level-1 tracklist match — allow disc_num=None (single-CD)
  by assuming disc=1; previously no tracklist title was ever applied to single-
  CD tracks because the guard required disc_num to be set
- music_enricher: register module in sys.modules before exec_module() so
  @dataclass definitions in jellyfin_playlist_generator work correctly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

music_enricher.py

@@ -55,6 +55,7 @@ def _run_jellyfin_generator(album_dir: Path, generator_path: Path) -> None:
     try:
         spec = importlib.util.spec_from_file_location("jellyfin_pg", generator_path)
         mod = importlib.util.module_from_spec(spec)  # type: ignore[arg-type]
+        sys.modules["jellyfin_pg"] = mod   # muss vor exec_module stehen (für @dataclass)
         spec.loader.exec_module(mod)  # type: ignore[union-attr]
 
         media_files = mod.collect_media_recursive(album_dir)