fix(lint): resolve eslint errors and warnings

- audioService: replace 'as any' with 'as unknown as AudioService' in
  resetInstance() to satisfy @typescript-eslint/no-explicit-any
- SongPage: add isReady to spacebar useEffect deps so the handler always
  sees the current readiness state
- useWaveform: add containerRef to deps (stable ref, safe to include);
  suppress exhaustive-deps for options.onReady with explanation — adding
  an un-memoized callback would cause initialization on every render

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

web/src/hooks/useWaveform.ts

@@ -77,7 +77,12 @@ export function useWaveform(
     };
 
     initializeAudio();
-  }, [options.url, options.songId, options.bandId]);
+  // containerRef is a stable ref object — safe to include.
+  // options.onReady is intentionally omitted: it's a callback that callers
+  // may not memoize, and re-running initialization on every render would be
+  // worse than stale-closing over it for the brief window after mount.
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [options.url, options.songId, options.bandId, containerRef]);
 
   const play = () => {
     audioService.play(options.songId ?? null, options.bandId ?? null)