thorvg 0.4.0

Tracks ThorVG 1.0.6 (via thorvg-sys 0.2). Picks up the upstream
API changes that affect the safe surface.

Changed (breaking)

• Depends on thorvg-sys 0.2 (bundling ThorVG 1.0.6).

Added

• LottieAnimation::set_audio_resolver / clear_audio_resolver and the
  AudioInfo borrowed view — safe wrappers over ThorVG 1.0.6's new
  Lottie audio-resolver callback, for synchronizing external audio
  playback with the animation timeline. The closure is heap-stored and
  unregistered on drop (same ownership model as the asset resolver).
  Experimental upstream.
• EngineOption::Aliased — re-introduced upstream in ThorVG 1.0.6
  (disables anti-aliased rendering). Marked experimental by upstream.
  The EngineOption enum is #[non_exhaustive], so this is additive.

Removed (breaking)

• LottieAnimation::assign — the underlying experimental
  tvg_lottie_animation_assign C API was removed in ThorVG 1.0.6.