feat(validations): merchant (bar/lavazh) ticket validations end-to-end

In-park merchants discharge customers' parking: a merchant user scans the
ticket on their device (/validate; validation:create + program↔user binding)
and applies their program — comp / first-N-minutes free / amount-off (capped,
typed at scan) / percent. All money stays at the booth: the quote folds live
validations in a canonical order (timeCredit → percent → fixed → comp, net
floors at 0, Σ lines ≡ gross − net), the payment records gross/discount and
CONSUMES the validation ids (an overstay's fresh period never re-applies
them), the receipt prints the gross → lines → net story, and the Z/X-report
carries discountTotalMinor leakage. Every apply/void is a signed, attributed
ledger event (refId = append-only void); program config is /setup/site master
data (Bar/Lavazh checkboxes + right-column panel, tabs when both) whose saves
sign config_change. Migration 0024 + reset-db drift-guard entries; 8 route
integration tests + priceSession fold suite.

See wiki/concepts/validation-discounts.md for the full design record.

Claude-Session: https://claude.ai/code/session_01YYkpEsLmoQPaize5ec3oUm

apps/web/src/BoothPayModal.tsx

@@ -383,6 +383,30 @@ export function BoothPayModal({ identity, onClose }: { identity: string; onClose
                   />
                 </div>
 
+                {/* Merchant validations (bar/lavazh): the gross fee + one line per
+                    discount — the Total below is the NET the customer pays. The lines
+                    ride the quote (SessionLookup.validationLines) and reprint on the
+                    receipt. See wiki/concepts/validation-discounts.md. */}
+                {!isSubscription &&
+                  (s.validationLines ?? []).length > 0 &&
+                  s.currency != null &&
+                  s.amountMinor != null && (
+                    <div className="rounded-term bg-term-panel-2 px-3 py-2 text-[0.75rem]">
+                      <div className="flex justify-between text-term-text">
+                        <span>{t("val.gross")}</span>
+                        <span className="tabular-nums">
+                          {formatMoney(s.grossMinor ?? s.amountMinor, s.currency)}
+                        </span>
+                      </div>
+                      {(s.validationLines ?? []).map((v, i) => (
+                        <div key={i} className="flex justify-between text-term-green">
+                          <span>{v.label}</span>
+                          <span className="tabular-nums">−{formatMoney(v.discountMinor, s.currency!)}</span>
+                        </div>
+                      ))}
+                    </div>
+                  )}
+
                 {/* Total — a subscription is prepaid (no amount) UNLESS it owes an
                     out-of-window window charge; then show that amount. For an overstay the
                     amount is the TOP-UP delta, not the whole stay. */}