Enhance audio verification features and improve code structure

- Added `ffmpeg` as a dependency in `flake.nix` and `package-cleanup.nix` for audio file property analysis.
- Updated `main.py` to include new functions for retrieving audio file properties using `ffprobe` and verifying audio matches with detailed confidence scoring.
- Refactored fingerprint comparison logic to improve accuracy and added logging for better traceability.
- Enhanced the `find_duplicate_singles` function to support audio verification results and confidence scores, providing clearer output for users.

flake.nix

@@ -52,11 +52,13 @@
             ))
             pkgs.black
             pkgs.chromaprint
+            pkgs.ffmpeg
           ];
           shellHook = ''
             echo "Python environment ready!"
             echo "Run: python src/main.py"
             echo "Format code with: black src/"
+            echo "Audio verification tools: ffprobe (ffmpeg), fpcalc (chromaprint)"
           '';
         };
       };