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

Fix Nebula Glide controls, leaderboard spam, and stale room codes

fix: address code review findings (AudioContext leak, stale closure, unused imports)

feat: port complex games (Glide, Merge) to V2

feat: port medium games (Memory, Wordle, Sequence) to V2

feat: port simple games (Reaction, Aim, Math, Typing) to V2