* refactor: remove built-in Spotify integration
Remove the Spotify adapter and all related configuration, replacing
the built-in integration with the plugin system. This deletes the
adapters/spotify package, removes Spotify config options (ID/Secret),
updates the default agents list from "deezer,lastfm,spotify" to
"deezer,lastfm", and cleans up all references across configuration,
metrics, logging, artwork caching, and documentation. Users with
Spotify config options will now see a warning that the options are
no longer available.
* feat: add ListenBrainz to list of default agents
Signed-off-by: Deluan <deluan@navidrome.org>
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Signed-off-by: Deluan <deluan@navidrome.org>