Implement full MVP: auth, HD wallet, Electrum client, deposits, bets, round/draw engine, payout, withdrawals, RBF, admin+audit

All 10 build-order stages complete and unit-tested (49 tests). Verified live on
mainnet: registration/address derivation, deposit crediting, a real 10 PLM bet
(broadcast + confirmed + change credited). A full round close->draw->payout
cycle was triggered live and was in progress at commit time. Withdrawal and RBF
bump are unit-tested but not yet exercised against a live broadcast. Known gaps
(scheduler doesn't resume mid-flight rounds after restart, payout has no retry,
no deployment setup, etc.) are documented in CLAUDE.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/rounds/config.py

@@ -0,0 +1,17 @@
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.db.models import RoundConfig
+
+
+async def get_round_config(session: AsyncSession) -> RoundConfig:
+    """Single-row operational config, lazily seeded from settings defaults on
+    first use. fee_address starts empty until an operator sets it (admin
+    endpoint, stage 10) — payouts must refuse to run until it's set."""
+    config = await session.scalar(select(RoundConfig))
+    if config is None:
+        config = RoundConfig(fee_address="", bet_amount_sats=settings.bet_amount_sats)
+        session.add(config)
+        await session.flush()
+    return config