feat: add MilkDrop and MilkDropWarp visualizers with audio-reactive e…

[sanderdw]

[0.15.0] - 2026-04-23

Added

• MilkDrop Warp visualizer – deep-tunnel feedback variant with vortex spiral warp, radial frequency bars, waveform spirals, concentric depth rings, and cross-shaped energy flare (Three.js/WebGL).
• MilkDrop visualizer – audio-reactive feedback-warp visualizer with ping-pong framebuffers, per-pixel motion vectors, kaleidoscopic symmetry, and psychedelic color cycling (Three.js/WebGL).
• Dependency bumps