Schema-v2 realtime SSE

Pass schemaVersion=2 and comma-separated topics. Public examples: market::book, market::trades, market::lifecycle, markets:all, trades:all and book-ticker:all. Private examples: user::orders, user::funding, user::settlements and user::account. Private semantic types include deposit., withdrawal., custody.transaction_changed, spendable_balance.changed, position.changed, claimable_balance.changed, reward.changed and payout.changed. Read authoritative topics, sources and replay floors from /v1/protocol/config.