- Add downloads.py: "Artist - Title.mp3" naming, no-overwrite dedupe,
configurable download_dir, progress and per-item callbacks.
- Save maximum metadata via tags.py (ID3v2.3, mutagen): artists, album
and album artist, track/disc, year/date, raw genre, label, duration,
explicit flag, cover 600x600, plain and synced lyrics (MTS then
LRCLIB), track URLs and Yandex/MTS ids.
- TUI/Qt: download current track and queue from the menu, "d" key in
lists, folder picker in settings; CLI download gains -d/--dir and
--no-tags.
- Add mutagen to requirements and document download/metadata in README.
- Fix MPRIS update_metadata crashing without dbus-next.
Reformat every module with autopep8 and hand-tune the remaining long
lines so that `flake8` passes with default settings (max line length
79). No behavior changes: long f-strings, messages, QSS/Textual CSS
rules and argument lists are only wrapped or split, an unused import
and an unused local are dropped, and dbus-next D-Bus signature
annotations carry targeted `# noqa` comments.
