Add Checkbox ETTN receipts for Nova Poshta COD waybills

Cashier creates an ETTN receipt in Checkbox bound to the TTN with payment
control; Checkbox fiscalizes it itself when the parcel is paid for.

- cash_registers (Fernet-encrypted license key / PIN) and receipts tables
- Checkbox HTTP client + stub (ETTN does not work on test registers)
- two-phase create via ARQ job, timeout reconciliation, cron status polling
- /receipts and /cash-registers API, audit records
- dashboard: per-order and bulk create, prepayment, cancel; cash registers page

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/receipts/money.ts

@@ -0,0 +1,27 @@
+/** Деньги на фронте приходят строками "1200.00"; в API чеков уходят integer-копейками. */
+
+export function toKopecks(value: string): number | null {
+  const normalized = value.trim().replace(/\s/g, '').replace(',', '.')
+  if (normalized === '') return 0
+  if (!/^\d+(\.\d{1,2})?$/.test(normalized)) return null
+  return Math.round(Number(normalized) * 100)
+}
+
+export function formatKopecks(kopecks: number): string {
+  return (kopecks / 100).toFixed(2)
+}
+
+/** Предоплата по умолчанию: сумма заказа − наложка НП (как считает бэкенд). */
+export function defaultPrepayment(total: string, cod: string | null): string {
+  if (!cod) return ''
+  const diff = (toKopecks(total) ?? 0) - (toKopecks(cod) ?? 0)
+  return diff > 0 ? formatKopecks(diff) : '0.00'
+}
+
+/** Проверка инварианта ЕТТН-чека: сумма − предоплата = наложка. */
+export function prepaymentMatches(total: string, cod: string | null, prepayment: string): boolean {
+  if (!cod) return false
+  const prep = toKopecks(prepayment)
+  if (prep === null) return false
+  return (toKopecks(total) ?? 0) - prep === toKopecks(cod)
+}

frontend/src/features/receipts/types.ts

@@ -0,0 +1,56 @@
+/**
+ * Типы, зеркалящие backend/app/schemas/receipts.py и `ReceiptStatus`
+ * (backend/app/db/models/receipt.py). Меняются синхронно с ними вручную.
+ */
+
+export type ReceiptStatus =
+  | 'pending'
+  | 'created'
+  | 'done'
+  | 'returned'
+  | 'receipt_error'
+  | 'cancelled'
+  | 'failed'
+
+export interface Receipt {
+  id: string
+  order_id: string
+  waybill_number: string
+  status: ReceiptStatus
+  total_amount: string
+  prepayment_amount: string
+  cod_amount: string
+  checkbox_ettn_id: string | null
+  checkbox_status: string | null
+  checkbox_receipt_id: string | null
+  error: string | null
+  created_at: string
+  last_checked_at: string | null
+}
+
+export interface ReceiptRequestItem {
+  order_id: string
+  /** null — предоплата = сумма заказа − наложка (считает бэкенд). */
+  prepayment_kopecks: number | null
+}
+
+export interface ReceiptCreateResponse {
+  created: Receipt[]
+  /** order_id → причина, по которой чек не создан. */
+  errors: Record<string, string>
+}
+
+export type Tone = 'delivered' | 'processing' | 'danger' | 'new'
+
+export const RECEIPT_STATUS: Record<ReceiptStatus, { label: string; tone: Tone }> = {
+  pending: { label: 'Отправляется', tone: 'new' },
+  created: { label: 'Ждёт оплаты', tone: 'processing' },
+  done: { label: 'Фискализирован', tone: 'delivered' },
+  returned: { label: 'Возврат посылки', tone: 'danger' },
+  receipt_error: { label: 'Ошибка фискализации', tone: 'danger' },
+  cancelled: { label: 'Отменён', tone: 'new' },
+  failed: { label: 'Не создан', tone: 'danger' },
+}
+
+/** Статусы, из которых чек можно отменить (см. services/receipts.cancel_receipt). */
+export const CANCELLABLE: ReadonlySet<ReceiptStatus> = new Set(['created', 'receipt_error'])