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/bets/confirmation.py

@@ -0,0 +1,19 @@
+from datetime import datetime, timezone
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.db.models import PendingTransaction, RoundParticipant
+from app.tx.confirmation import register_handler
+
+
+async def _on_bet_confirmed(session: AsyncSession, pending: PendingTransaction) -> None:
+    participant = await session.scalar(
+        select(RoundParticipant).where(RoundParticipant.bet_txid == pending.current_txid)
+    )
+    if participant is not None and participant.status == "broadcast":
+        participant.status = "confirmed"
+        participant.confirmed_at = datetime.now(timezone.utc)
+
+
+register_handler("bet", _on_bet_confirmed)