feat: GnuDB fallback with retries when abcde CDDB lookup returns nothing

- New module cddb.py: direct GnuDB/FreeDB HTTP lookup using CDDB protocol,
  with same retry+random-delay logic as MusicBrainz barcode lookup
- get_discid() reads disc fingerprint via cd-discid before ripping
- If abcde returns no CDDB track data, lookup_by_discid() queries GnuDB
  directly (up to 3 retries, 2-6 s random pause between attempts)
- TrackInfo moved from ripper.py to models.py to break circular import
  (cddb.py and ripper.py both use TrackInfo)

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

src/musiksammlung/ripper.py

@@ -6,14 +6,15 @@ import logging
 import re
 import subprocess
 from pathlib import Path
-from typing import NamedTuple
 
 from pydantic import BaseModel
 
+from musiksammlung.cddb import get_discid, lookup_by_discid
 from musiksammlung.config import AudioFormat
 from musiksammlung.models import Album as AlbumModel
 from musiksammlung.models import Disc as DiscModel
 from musiksammlung.models import Track as TrackModel
+from musiksammlung.models import TrackInfo
 from musiksammlung.musicbrainz import lookup_by_barcode
 
 logger = logging.getLogger(__name__)
@@ -22,14 +23,6 @@ logger = logging.getLogger(__name__)
 _ANSI_ESC = re.compile(r"(\x1b|\^)\[[\d;]*[A-Za-z@]?")
 
 
-class TrackInfo(NamedTuple):
-    """Track information from abcde."""
-
-    track_number: int
-    artist: str
-    title: str
-
-
 class RipperConfig(BaseModel):
     """Configuration for ripping process."""
 
@@ -331,6 +324,9 @@ def _rip_with_abcde(
     if use_pipes:
         cmd.append("-P")
 
+    # Disc-Fingerprint vor dem Ripping holen (für GnuDB-Fallback)
+    discid_line = get_discid(device)
+
     print(f"\n  Command: {' '.join(cmd)}", flush=True)
     logger.info("Starting abcde: %s", " ".join(cmd))
 
@@ -355,6 +351,14 @@ def _rip_with_abcde(
         else:
             print("\n  CDDB: no track data found", flush=True)
             logger.warning("CDDB lookup returned no track data")
+            # Fallback: GnuDB direkt anfragen (mit Retries + Zufallspause)
+            if discid_line:
+                print("  GnuDB-Fallback: direkter Lookup mit Retries...", flush=True)
+                tracks = lookup_by_discid(discid_line) or None
+                if tracks:
+                    print(f"  GnuDB: {len(tracks)} Tracks gefunden", flush=True)
+                else:
+                    print("  GnuDB: kein Treffer.", flush=True)
 
     # Extract track files from abcde's temp dir into output_dir (flat)
     audio_files = _extract_tracks(output_dir, audio_format)