fix: build error in nextSong + apply romaji overrides to downloads

- Fix missing closing brace for `if (ni >= 0...)` in nextSong — the removed
  `else { _nsBridge('next') }` left the inner if-block unclosed, causing
  vite/rollup to reject player.js as invalid JS
- Apply romaji override map to iTunes (executeDownload) and Spotify
  (executeSpotifyDownload) download payloads — sends artistSort/albumArtistSort/
  titleSort/albumSort fields so the backend writes correct sort tags to the
  downloaded file and can organize into the right artist folder

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

src/player.js

@@ -716,6 +716,7 @@ export function nextSong() {
       // Explicit index prevents desync when JS and native queue pointers diverge.
       _nsBridge('seekToIndex', ni, 0);
       _nsBridge('play');
+    }
     // else: ni = -1 means end of queue with no repeat — let ExoPlayer stop naturally.
     if (S.radioMode && S.queue.length - S.qIdx < 5) fillRadioQueue();
     return;