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/api.ts

@@ -7,7 +7,7 @@
 
 import { logFailedRequest } from "./lib/logger.js";
 import { apiUrl } from "./lib/origin.js";
-import type { AppLogRecord } from "@parking/shared";
+import type { AppLogRecord, ValidationLine, ValidationMode } from "@parking/shared";
 
 const CSRF_COOKIE = "parking_csrf";
 const CSRF_HEADER = "X-CSRF-Token";
@@ -1301,6 +1301,11 @@ export interface SessionLookup {
   subscriptionHolder: string | null;
   /** Advisory licence plate recognized for this session (ANPR). Null when none. */
   plate: string | null;
+  /** Merchant validations folded into `amountMinor` (which is NET): pre-discount fee,
+   *  total taken off, and the per-validation lines. See validation-discounts.md. */
+  grossMinor: number | null;
+  discountMinor: number | null;
+  validationLines: ValidationLine[];
 }
 
 /** Look up a ticket/session for the booth modal (entry/exit, paid, amount owed). */
@@ -1475,3 +1480,88 @@ export function updatePresenceBypass(patch: { radar?: boolean; camera?: boolean
 export function setCapacity(capacity: number | null): Promise<SiteConfig> {
   return saveSiteConfig({ capacity });
 }
+
+// --- Merchant validations (bar / lavazh) -----------------------------------
+// The merchant is VALIDATION-ONLY: they scan the ticket on their device and apply
+// their program; the booth settles NET of the applied validations and prints the
+// detailed receipt. Program config lives on /setup/site. See validation-discounts.md.
+
+export type { ValidationLine, ValidationMode } from "@parking/shared";
+
+/** An admin-composed program (mirrors the server row + its bound users). */
+export interface ValidationProgramView {
+  id: string;
+  name: string;
+  mode: ValidationMode;
+  minutes: number | null;
+  percent: number | null;
+  maxAmountMinor: number | null;
+  maxPerDay: number | null;
+  active: boolean;
+  userIds: string[];
+}
+
+/** A validation applied to a session, with its lifecycle state. */
+export interface AppliedValidationView {
+  eventId: string;
+  occurredAt: string;
+  programId: string;
+  label: string;
+  mode: ValidationMode;
+  minutes?: number;
+  amountMinor?: number;
+  percent?: number;
+  operator: string | null;
+  voided: boolean;
+  consumedBy: string | null;
+}
+
+/** The merchant screen's minimal session view — deliberately no money data. */
+export interface ValidationSessionView {
+  identity: string;
+  found: boolean;
+  open: boolean;
+  enteredAt: string | null;
+  subscription: boolean;
+  validations: AppliedValidationView[];
+}
+
+/** All programs + bound users (the /setup/site panel). site:read. */
+export function fetchValidationPrograms(): Promise<{ programs: ValidationProgramView[] }> {
+  return apiFetch("/api/validation/programs");
+}
+
+/** Upsert a program's config + binding set (site:update; signs a config_change). */
+export function saveValidationProgram(
+  id: string,
+  body: Omit<ValidationProgramView, "id">,
+): Promise<ValidationProgramView> {
+  return apiFetch(`/api/validation/programs/${encodeURIComponent(id)}`, {
+    method: "PUT",
+    body: JSON.stringify(body),
+  });
+}
+
+/** MY bound, active programs (the merchant screen). validation:create. */
+export function fetchMyValidationPrograms(): Promise<{ programs: Omit<ValidationProgramView, "userIds">[] }> {
+  return apiFetch("/api/validation/mine");
+}
+
+/** Merchant lookup of a scanned ticket (no money data). validation:create. */
+export function fetchValidationSession(identity: string): Promise<ValidationSessionView> {
+  return apiFetch(`/api/validation/session/${encodeURIComponent(identity)}`);
+}
+
+/** Apply my program to a ticket (signed, attributed). `amountMinor` only for fixed mode. */
+export function applyValidation(body: {
+  identity: string;
+  programId: string;
+  amountMinor?: number;
+}): Promise<{ ok: true; eventId: string; label: string }> {
+  return apiFetch("/api/validation/apply", { method: "POST", body: JSON.stringify(body) });
+}
+
+/** Void my own UNUSED validation (append-only correction). */
+export function voidValidation(body: { eventId: string; identity: string }): Promise<{ ok: true }> {
+  return apiFetch("/api/validation/void", { method: "POST", body: JSON.stringify(body) });
+}