feat(booth): pay-on-foot at the booth — ticket lookup, pay, exit, voucher, snapshots

Backend: PayStation.lookup (session view + quote in one read); ExitFlow.exitForBooth
reuses the reader path's paid+grace validation (no booth-only unpaid bypass) and
signs vehicle_exit + pulses an exit relay; printExitVoucher reprints the paid ticket
id barcode; site_config.exit_voucher_default (migration 0002) drives the default.
Routes: GET /api/session/:id, POST /api/exit, POST /api/voucher.

Web: BoothPayModal (entry/now/duration/total, tender, 'Printo biletë dalje'),
SnapshotStrip (entry/exit evidence), api.ts client fns, SiteSettings toggle.

packages/db/src/schema.ts

@@ -151,6 +151,15 @@ export const siteConfig = sqliteTable("site_config", {
   phone: text("phone"),
   /** Contact email. */
   email: text("email"),
+  /** Default for the booth pay modal's "print exit ticket" checkbox. Site-wide
+   *  because it's booth GEOGRAPHY: when the booth is far from the exit, the
+   *  customer pays at the booth and self-exits later by scanning a printed exit
+   *  voucher (= the ticket id reprinted, now paid). When near the exit, the booth
+   *  opens the barrier directly. The operator may still override per transaction.
+   *  Stored 0/1 (SQLite has no bool). See wiki/concepts/booth-exit-flow.md. */
+  exitVoucherDefault: integer("exit_voucher_default", { mode: "boolean" })
+    .notNull()
+    .default(false),
   updatedAt: text("updated_at")
     .notNull()
     .default(sql`(current_timestamp)`),