Move all business/round parameters into DB config, out of env entirely

RoundConfig gains round_duration_seconds, round_cooldown_seconds,
min_amount_sats, fee_rate_sat_vb and rbf_timeout_seconds (plus a
hardcoded default for the pre-existing bet_amount_sats) as column
defaults on the model itself — get_round_config no longer seeds from
Settings at all. Every call site that read these from settings
(scheduler, bets, withdrawals, rounds service/route, RBF bumper) now
reads the DB-backed RoundConfig instead.

app/config.py now holds only true env-driven infra/secrets (database
URL, Electrum connection, master key, JWT, admin token) — no business
parameter has an env var anymore, matching an explicit decision to drop
the "seed from settings" indirection entirely rather than keep a env
fallback nobody should rely on.

Migration backfills the existing round_config row via server_default
(matching the old settings defaults) then drops the default, so future
rows go through the ORM/model defaults instead of a stale constant.

Tests updated: should_bump's timeout_seconds is now required (no
settings fallback); test_scheduler.py seeds a RoundConfig row directly
instead of monkeypatching settings; test_withdrawals.py and
test_rounds_service.py use local constants mirroring the model
defaults instead of reading them off settings.

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

app/db/models.py

@@ -74,15 +74,22 @@ class RoundParticipant(Base):
 class RoundConfig(Base):
     """Single-row operational config, DB-backed so it's editable without a redeploy.
 
-    round_duration is intentionally NOT here: it stays env-var-driven per spec.
-    Don't move it here without an explicit decision to change that.
-    """
+    Everything business/round-related lives here (round timing, bet amount, fee
+    rate, RBF timeout, minimum amount) so an operator can tune it live. Secrets
+    and infra wiring (master key, JWT secret, Electrum host, admin token,
+    database URL) deliberately stay env-var-driven — those require a restart
+    anyway and aren't safe to hot-swap."""
 
     __tablename__ = "round_config"
 
     id: Mapped[int] = mapped_column(primary_key=True)
     fee_address: Mapped[str] = mapped_column(String(128))
-    bet_amount_sats: Mapped[int] = mapped_column(BigInteger)
+    bet_amount_sats: Mapped[int] = mapped_column(BigInteger, default=1_000_000_000)
+    round_duration_seconds: Mapped[int] = mapped_column(default=600)
+    round_cooldown_seconds: Mapped[int] = mapped_column(default=30)
+    min_amount_sats: Mapped[int] = mapped_column(BigInteger, default=100_000_000)
+    fee_rate_sat_vb: Mapped[int] = mapped_column(default=1)
+    rbf_timeout_seconds: Mapped[int] = mapped_column(default=900)
     updated_at: Mapped[datetime] = mapped_column(default=utcnow, onupdate=utcnow)