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

packages/devices/src/drivers/printer-escpos.ts

@@ -202,6 +202,9 @@ const STR = {
   tenderCard: "Kartë",
   /** "Paid:" amount label (precedes the large total). */
   amountLabel: "PAGUAR",
+  /** Merchant-validation lines: the pre-discount fee + one line per discount. */
+  gross: (v: string) => `Tarifa:   ${v}`,
+  discount: (label: string, v: string) => `${label}: -${v}`,
   /** Walk-back grace emphasis (voucher mode) — two short lines that each fit the
    *  80mm width, so neither wraps mid-word. */
   graceLines: (min: number): readonly string[] => [
@@ -413,6 +416,16 @@ export function renderReceipt(data: ReceiptData): Buffer {
     line(
       STR.tender(data.tender === "card" ? STR.tenderCard : STR.tenderCash),
     ),
+    // Merchant validations: gross fee + one line per discount, so the customer sees
+    // the full gross → discounts → net story (the big amount below is the NET).
+    ...(data.validationLines?.length
+      ? [
+          line(STR.gross(money(data.grossMinor ?? data.amountMinor, data.currency))),
+          ...data.validationLines.map((v) =>
+            line(STR.discount(v.label, money(v.discountMinor, data.currency))),
+          ),
+        ]
+      : []),
     line(),
     // The amount, large and centred.
     ALIGN_CENTER,

packages/devices/src/interfaces.ts

@@ -275,6 +275,11 @@ export interface ReceiptData {
   readonly voucher: boolean;
   /** Minutes the customer has to reach the exit after paying (voucher mode only). */
   readonly graceExitMin?: number | null;
+  /** Merchant validations (bar/lavazh): the PRE-discount fee and the per-validation
+   *  lines. When present, `amountMinor` is the NET actually paid and the receipt
+   *  shows the full gross → discounts → net story. See validation-discounts.md. */
+  readonly grossMinor?: number | null;
+  readonly validationLines?: readonly { label: string; discountMinor: number }[];
   readonly header?: TicketHeader;
 }