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/SiteSettings.tsx

@@ -1,6 +1,16 @@
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
-import { fetchOccupancy, fetchSiteConfig, saveSiteConfig, type Occupancy, type SiteConfig } from "./api.js";
+import {
+  fetchOccupancy,
+  fetchSiteConfig,
+  fetchValidationPrograms,
+  saveSiteConfig,
+  saveValidationProgram,
+  type Occupancy,
+  type SiteConfig,
+  type ValidationProgramView,
+} from "./api.js";
+import { STATIONS, ValidationStationsPanel, defaultProgram, type StationId } from "./ValidationSetup.js";
 
 // Live occupancy + capacity + park metadata. Occupancy is shown to everyone (it's a
 // fold over the signed ledger); capacity and the metadata fields are admin-editable.
@@ -28,12 +38,21 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
   const [reserveSubs, setReserveSubs] = useState(false);
   const [anprEntry, setAnprEntry] = useState(true);
   const [msg, setMsg] = useState<string | null>(null);
+  // Merchant-validation programs (bar / lavazh). The checkboxes below toggle a
+  // station's `active` (persisted at once — each flip signs a config_change); the
+  // right-column panel edits the enabled stations. See validation-discounts.md.
+  const [programs, setPrograms] = useState<ValidationProgramView[]>([]);
 
   function reload() {
     fetchOccupancy().then(setOcc).catch(() => {});
   }
   useEffect(() => {
     reload();
+    if (canEdit) {
+      fetchValidationPrograms()
+        .then((r) => setPrograms(r.programs))
+        .catch(() => {});
+    }
     fetchSiteConfig()
       .then((c) => {
         setCapInput(c.capacity == null ? "" : String(c.capacity));
@@ -45,7 +64,23 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
         setMeta(m);
       })
       .catch(() => {});
-  }, []);
+  }, [canEdit]);
+
+  /** Flip a merchant station's checkbox: persist `active` at once (a signed
+   *  config_change server-side), creating the well-known row with comp defaults on
+   *  the first enable. Config details are edited in the right-column panel. */
+  async function toggleStation(id: StationId, active: boolean) {
+    const existing = programs.find((p) => p.id === id);
+    const body = existing
+      ? { ...existing, active }
+      : { ...defaultProgram(id, t(id === "bar" ? "val.enableBar" : "val.enableLavazh")), active };
+    try {
+      const saved = await saveValidationProgram(id, body);
+      setPrograms((ps) => [...ps.filter((p) => p.id !== id), saved]);
+    } catch (e) {
+      setMsg((e as Error).message);
+    }
+  }
 
   async function save() {
     setMsg(null);
@@ -68,7 +103,8 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
   }
 
   return (
-    <section className="card mt-6 max-w-md p-4">
+    <div className="mt-6 flex flex-wrap items-start gap-6">
+    <section className="card w-full max-w-md p-4">
       <div className="flex flex-wrap items-center gap-1.5 text-[0.8125rem]">
         <strong className="uppercase tracking-wider text-term-muted">{t("site.occupancy")}</strong>
         {occ == null ? (
@@ -127,6 +163,23 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
               <span className="hint block">{t("site.anprEntryHint")}</span>
             </span>
           </label>
+          <div className="border-t border-term-border pt-3 text-[0.6875rem] uppercase tracking-wider text-term-muted">
+            {t("val.sectionTitle")}
+          </div>
+          <span className="hint -mt-2">{t("val.sectionHint")}</span>
+          <div className="flex gap-6">
+            {STATIONS.map((id) => (
+              <label key={id} className="flex items-center gap-2 text-[0.75rem] text-term-text">
+                <input
+                  type="checkbox"
+                  className="accent-term-amber"
+                  checked={programs.find((p) => p.id === id)?.active ?? false}
+                  onChange={(e) => toggleStation(id, e.target.checked)}
+                />
+                {t(id === "bar" ? "val.enableBar" : "val.enableLavazh")}
+              </label>
+            ))}
+          </div>
           <div className="border-t border-term-border pt-3 text-[0.6875rem] uppercase tracking-wider text-term-muted">
             {t("site.parkDetails")}
           </div>
@@ -158,5 +211,12 @@ export function SiteSettings({ canEdit }: { canEdit: boolean }) {
         </div>
       )}
     </section>
+    {canEdit && (
+      <ValidationStationsPanel
+        programs={programs}
+        onSaved={(p) => setPrograms((ps) => [...ps.filter((x) => x.id !== p.id), p])}
+      />
+    )}
+    </div>
   );
 }