Add YouTube ID detection and metadata lookup via yt-dlp

- Extract 11-char YouTube video IDs from audio filenames
- Fetch title, uploader, chapters via yt-dlp (--dump-json)
- Use chapters as tracklist when no .txt tracklist is available
- Store yt_title / yt_uploader in AlbumHints for LLM prompt context
- Fall back to YouTube video title as track title for single-file albums

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

metadata_resolver.py

@@ -213,6 +213,8 @@ def _build_resolve_prompt(hints: AlbumHints, partial: Dict) -> str:
         f"Hinweis Künstler/Titel (aus Verzeichnis, kann vertauscht oder falsch sein): "
         f"{hints.dir_artist or '?'} / {hints.dir_album or partial.get('album', '?')}\n"
         f"Jahr: {hints.dir_year or partial.get('year', 'unbekannt')}\n"
+        + (f"YouTube-Videotitel: {hints.yt_title}\n" if hints.yt_title else "")
+        + (f"YouTube-Uploader/Kanal: {hints.yt_uploader}\n" if hints.yt_uploader else "")
         + (f"Tracklist-Kopf (Label/Jahr/Albumtitel):\n{tracklist_header}\n\n" if tracklist_header else "")
         + f"Tracks:\n{tracks_summary}\n\n"
         'Antworte NUR mit einem JSON-Objekt (null wenn unbekannt):\n'
@@ -354,9 +356,17 @@ def resolve(
         genre = genre or t.existing_tags.get("genre")
         label = label or t.existing_tags.get("label") or t.existing_tags.get("organization")
 
+    # YouTube-Metadaten als zusätzliche Hinweise (Uploader → Künstler, Titel → Album/Track)
+    if hints.yt_uploader and not artist:
+        artist = hints.yt_uploader
+    if hints.yt_title and not album:
+        album = hints.yt_title
+
     if artist or album:
         confidence += 0.05
         sources.append("local-hints")
+    if hints.yt_title or hints.yt_uploader:
+        sources.append("youtube")
 
     # AcoustID fingerprinting
     fp_mbids: Dict[str, List[str]] = {}