feat: add similar songs functionality in agents, and Instant Mix (song-based) to UI (#4919)

* refactor: rename ArtistRadio to SimilarSongs for clarity and consistency

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

* feat: implement GetSimilarSongsByTrack and related functionality for song similarity retrieval

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

* feat: enhance GetSimilarSongsByTrack to include artist and album details and update tests

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

* feat: enhance song matching by implementing title and artist filtering in loadTracksByTitleAndArtist

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

* test: add unit tests for song matching functionality in provider

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

* refactor: extract song matching functionality into its own file

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

* docs: clarify similarSongsFallback function description in provider.go

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

* refactor: initialize result slice for songs with capacity based on response length

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

* refactor: simplify agent method calls for retrieving images and similar songs

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

* refactor: simplify agent method calls for retrieving images and similar songs

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

* refactor: remove outdated comments in GetSimilarSongs methods

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

* fix: use composite key for song matches to handle duplicates by title and artist

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

* refactor: consolidate expectations setup for similar songs tests

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

* feat: add instant mix action to song context menu and update translations

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

* fix(provider): handle unknown entity types in GetSimilarSongs

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

* refactor: move playSimilar action to playbackActions and streamline song processing

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

* format

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

* feat: enhance instant mix functionality with loading notification and shuffle option

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

* feat: implement fuzzy matching for similar songs based on configurable threshold

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

* refactor: implement track matching with multiple specificity levels

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

* refactor: enhance track matching by implementing unified scoring with specificity levels

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

* feat: enhance deezer top tracks result with album

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

* feat: enhance track matching with fuzzy album similarity for improved scoring

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

* docs: document multi-phase song matching algorithm with detailed scoring and prioritization

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

---------

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

adapters/lastfm/client.go

@@ -95,6 +95,19 @@ func (c *client) artistGetTopTracks(ctx context.Context, name string, limit int)
 	return &response.TopTracks, nil
 }
 
+func (c *client) trackGetSimilar(ctx context.Context, name, artist string, limit int) (*SimilarTracks, error) {
+	params := url.Values{}
+	params.Add("method", "track.getSimilar")
+	params.Add("track", name)
+	params.Add("artist", artist)
+	params.Add("limit", strconv.Itoa(limit))
+	response, err := c.makeRequest(ctx, http.MethodGet, params, false)
+	if err != nil {
+		return nil, err
+	}
+	return &response.SimilarTracks, nil
+}
+
 func (c *client) GetToken(ctx context.Context) (string, error) {
 	params := url.Values{}
 	params.Add("method", "auth.getToken")