feat(admin): operations console, fees wired into payouts

Fees now flow through settlement. The payout and the deduction are posted
as separate ledger transactions rather than netted, so a player's history
shows the full win and the charge as itemised lines instead of a quietly
smaller win.

The admin console shows treasury, liability, revenue, every posting,
every round, and risk flags. Auth is a constant-time token compare and
the surface is not mounted at all unless ARCADE_ADMIN_TOKEN is set, so a
default deployment has no admin endpoint to attack. The token lives in
browser memory only.

It is read-only over game outcomes by design: seeds show only after
settlement and nothing can alter a crash point. A control that could
would make the fairness proof a lie.

The console immediately found a real bug: 343 unresolved rounds, because
the reconciler only considered rounds with bets and abandoned empty ones
accumulated forever, burying the signal. Now cleared automatically.

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

migrations/0005_fees.sql

@@ -0,0 +1,9 @@
+-- Fee breakdown per bet, so a settled round records not just what was paid but
+-- what was deducted and why. The ledger already carries the money; this makes
+-- the split queryable for reporting without re-deriving it.
+
+ALTER TABLE bets ADD COLUMN rake_msat     BIGINT NOT NULL DEFAULT 0;
+ALTER TABLE bets ADD COLUMN rounding_msat BIGINT NOT NULL DEFAULT 0;
+
+ALTER TABLE bets ADD CONSTRAINT bet_fees_non_negative
+    CHECK (rake_msat >= 0 AND rounding_msat >= 0);