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/api/routes/users.py

@@ -0,0 +1,18 @@
+from fastapi import APIRouter, Depends
+from pydantic import BaseModel
+
+from app.auth.dependencies import get_current_user
+from app.db.models import User
+
+router = APIRouter(prefix="/users", tags=["users"])
+
+
+class MeResponse(BaseModel):
+    username: str
+    address: str
+    balance_sats: int
+
+
+@router.get("/me", response_model=MeResponse)
+async def me(user: User = Depends(get_current_user)) -> MeResponse:
+    return MeResponse(username=user.username, address=user.address, balance_sats=user.cached_balance_sats)