Iridescent dotted map and 3D globe look

Iridescent applies a Fresnel-driven HSV cycle across the dot field, with procedural sparkle on top. Depending on the motion setting it looks like holographic foil, pearlescent paint or fish-scale shimmer. The same foil look shows up in Y2K-revival branding and credit-card marketing. The hue cycles over time (paused under prefers-reduced-motion), and cellSize sets the sparkle density. Use it with the globe view for hero graphics.