chore: remove dead code to eliminate all compiler warnings

- Remove unused get_artist() (replaced by get_artist_page())
- Remove unused Format::label(), Format::all()
- Remove unused QwsTokenResponse and QwsToken structs
- Remove unused PlayerCommand::Seek (seeking uses atomics directly)
- Remove unused PlayerState::Stopped, TrackInfo::format
- Remove unused PlayerStatus::get_current_track()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

rust/src/api/client.rs

@@ -255,20 +255,6 @@ impl QobuzClient {
 
     // --- Artist ---
 
-    pub async fn get_artist(&self, artist_id: i64) -> Result<ArtistDto> {
-        let resp = self
-            .get_request("artist/get")
-            .query(&[
-                ("artist_id", artist_id.to_string()),
-                ("extra", "albums".to_string()),
-                ("albums_limit", "200".to_string()),
-            ])
-            .send()
-            .await?;
-        let body = Self::check_response(resp).await?;
-        Ok(serde_json::from_value(body)?)
-    }
-
     pub async fn get_artist_page(&self, artist_id: i64) -> Result<Value> {
         let resp = self
             .get_request("artist/page")