fix: pin GaussianSplats3D CDN to 0.4.7 — version 0.5.0 does not exist on npm

fix: replace CORS-blocked HEAD probe with direct SPZ load + PLY fallback on error

feat: prefer SPZ over PLY — 10-20x smaller, SH3 preserved, falls back to PLY

fix: cupr-001 PLY path — use top-level 50MB file not 159MB subdirectory

feat: V0 splat viewer — 5 mineral specimens, GaussianSplats3D renderer, public datasets

feat: V0 splat viewer — 5 mineral specimens, GaussianSplats3D renderer

initial commit