feat(deezer): Add artist bio, top tracks, related artists and language support (#4720)

* feat(deezer): add functions to fetch related artists, biographies, and top tracks for an artist

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(deezer): add language support for Deezer API client

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(deezer): Use GraphQL API for translated biographies

The previous implementation scraped the __DZR_APP_STATE__ from HTML,
which only contained English content. The actual biography displayed
on Deezer's website comes from their GraphQL API at pipe.deezer.com,
which properly respects the Accept-Language header and returns
translated content.

This change:
- Switches from HTML scraping to the GraphQL API
- Uses Accept-Language header instead of URL path for language
- Updates tests to match the new implementation
- Removes unused HTML fixture file

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor(deezer): move JWT token handling to a separate file for better organization

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(deezer): enhance JWT token handling with expiration validation

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor(deezer): change log level for unknown agent warnings from Warn to Debug

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(deezer): reduce JWT token expiration buffer from 10 minutes to 1 minute

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

core/agents/deezer/deezer.go

@@ -12,6 +12,7 @@ import (
 	"github.com/navidrome/navidrome/log"
 	"github.com/navidrome/navidrome/model"
 	"github.com/navidrome/navidrome/utils/cache"
+	"github.com/navidrome/navidrome/utils/slice"
 )
 
 const deezerAgentName = "deezer"
@@ -32,7 +33,7 @@ func deezerConstructor(dataStore model.DataStore) agents.Interface {
 		Timeout: consts.DefaultHttpClientTimeOut,
 	}
 	cachedHttpClient := cache.NewHTTPClient(httpClient, consts.DefaultHttpClientTimeOut)
-	agent.client = newClient(cachedHttpClient)
+	agent.client = newClient(cachedHttpClient, conf.Server.Deezer.Language)
 	return agent
 }
 
@@ -88,6 +89,56 @@ func (s *deezerAgent) searchArtist(ctx context.Context, name string) (*Artist, e
 	return &artists[0], err
 }
 
+func (s *deezerAgent) GetSimilarArtists(ctx context.Context, _, name, _ string, limit int) ([]agents.Artist, error) {
+	artist, err := s.searchArtist(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+
+	related, err := s.client.getRelatedArtists(ctx, artist.ID)
+	if err != nil {
+		return nil, err
+	}
+
+	res := slice.Map(related, func(r Artist) agents.Artist {
+		return agents.Artist{
+			Name: r.Name,
+		}
+	})
+	if len(res) > limit {
+		res = res[:limit]
+	}
+	return res, nil
+}
+
+func (s *deezerAgent) GetArtistTopSongs(ctx context.Context, _, artistName, _ string, count int) ([]agents.Song, error) {
+	artist, err := s.searchArtist(ctx, artistName)
+	if err != nil {
+		return nil, err
+	}
+
+	tracks, err := s.client.getTopTracks(ctx, artist.ID, count)
+	if err != nil {
+		return nil, err
+	}
+
+	res := slice.Map(tracks, func(r Track) agents.Song {
+		return agents.Song{
+			Name: r.Title,
+		}
+	})
+	return res, nil
+}
+
+func (s *deezerAgent) GetArtistBiography(ctx context.Context, _, name, _ string) (string, error) {
+	artist, err := s.searchArtist(ctx, name)
+	if err != nil {
+		return "", err
+	}
+
+	return s.client.getArtistBio(ctx, artist.ID)
+}
+
 func init() {
 	conf.AddHook(func() {
 		if conf.Server.Deezer.Enabled {