feat: remove Supabase, bundle questions locally, use JSON DB + API

feat(spark): add Challenge a Friend + shareable verdict card

feat: add Spark Micro-Debate Arena

feat: replace Master's Lair with WebGL cosmic descent

feat: fix question system + add HF Spaces deployment

feat: install lucide-react + canvas-confetti, add nebula CSS foundation

feat: scaffold Next.js 15 + Tailwind v4 + Vitest + Supabase deps