fix: loop-B adversarial findings — tip-type double-charge, tip-refund capacity, loyalty stamp farming, gate ordering, auth amplification, admin audit log

Loop B restart (money/security/dup-mod adversarial) fixes:
- CRITICAL: CreateTerminalPayment rejects payment_type='tip' (mirrors CreateBookingPayment) — a tip-typed admin charge no longer records the FULL amount as a tip and double-collects (all is-paid computations exclude tip rows)
- HIGH: tip refunds can no longer re-open booking capacity — refunded_total subqueries filter payment_type <> 'tip' (service.go) and RefundPayment rejects tip rows
- MEDIUM: loyalty-stamp farming closed — stamp award once-per-booking via loyalty_stamp_awarded_at column (init-script.sql) + existing same-day guard
- MEDIUM: CreateTipPayment/CreateBookingPayment 2FA gates moved AFTER the idempotency completed-dedup (code consumed only on new money paths; terminal path already correct) — lost-response retries return the completed payment instead of 400
- MEDIUM: replayRescueLowerBoundSkew widened to 5m (DB-clock-skew stranded originals now rescued)
- MEDIUM-1: verifyFamilyAlive DB amplification reduced via 30s bounded family-alive cache; admin route group rate-limited
- MEDIUM-3: admin saved-card charges now write admin_audit_log (handlers.go helper + till); [2FA] log line decoupled from user identity
- LOW-1: logout scoped to the presented token's family (no cross-session kill)
- LOW-2: refresh-reuse grace widened for same-IP replays
- LOW-4: squareEnvironmentMismatch enforced for empty env
- LOW-5: uuid.ts hard-fails on Math.random fallback (crypto.randomUUID)
- Cash/giftcard tip-enabled overflow mirrors the card-terminal carve

26/26 backend packages; 72/72 frontend tests + build; env-docs 41/41.

init-scripts/init-script.sql

@@ -388,7 +388,15 @@ CREATE TABLE bookings (
     updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     created_by CHAR(12),
     idempotency_key VARCHAR(64) UNIQUE,
-    out_of_hours BOOLEAN NOT NULL DEFAULT FALSE
+    out_of_hours BOOLEAN NOT NULL DEFAULT FALSE,
+    -- Once-only loyalty-stamp marker (Loop B MEDIUM — stamp farming via refund
+    -- + re-charge): the stamp is awarded at most ONCE per booking, no matter
+    -- how many times the booking is re-completed. A refund never moves the
+    -- booking out of 'in_progress', so a re-payment re-completes it; without
+    -- this marker each in_progress→completed transition would mint another
+    -- stamp with no net merchant cash flow. Set by
+    -- ApplyBookingCompletionSideEffects only when a stamp is actually awarded.
+    loyalty_stamp_awarded_at TIMESTAMPTZ
 );
 
 CREATE INDEX idx_bookings_userid ON bookings(user_id);