Port the boolab FX controls: localStorage-backed Density, Speed, and Opacity sliders in the theme settings, shown when a canvas-background theme is active (Density is matrix-rain-only). Speed is a multiplier over each field's native base; values feed MatrixRain / NeonField live. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>