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

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

feat(spark): complete debate arena rework to conversational flow

fix(spark): update downstream components for new RoundData field names

feat: add full debate transcript and expandable rounds to verdict

feat(spark): update debate room and components for spectrum redesign

feat(spark): DB queries, API routes, and UI components for spectrum redesign

feat: add speech-to-text mic button for debate arguments

feat: redesign judge to be qualitative instead of numeric categories

feat: add Spark Micro-Debate Arena