Revert Space to pre-change live-compute leaderboard (state b49e5fb685)

Update leaderboard to latest paper tables

Add Track 3 (forecasting) leaderboard section: live skill/rank/fair-skill vs seasonal_naive; pin openmhc@991caf5

Compute real MAPD fair-skill live; bump openmhc pin to main@bd5a102

Use the real MyHeartCounts heart logo in the wordmark + favicon

Fix build: install git for VCS pip install; cap pandas<3

Replace JSON API with self-rendering imputation leaderboard (computed live from substrate)

Sync from website repo @ 54e38ed7

Bring up FastAPI leaderboard backend