Add CRM order queue: live sync, view modal, receipt tabs, delete

Wires the CRM (exoCRM GetOrders) into the dashboard as a locally
persisted order queue instead of the previous static mockup:

- CrmClient Protocol + ExoCrmClient/StubCrmClient for the CRM's
  signed JSON-RPC API
- Order model + migration, synced from CRM on each queue view;
  soft-deleted orders stay hidden across re-syncs
- GET/DELETE /api/v1/orders with "no receipt"/"receipt issued" tabs
  (the latter is empty until Checkbox fiscalization lands)
- Dashboard: real order list, item-detail modal, tab switcher,
  one-click delete

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/api/orders.ts

@@ -0,0 +1,10 @@
+import { apiFetch } from '@/api/client'
+import type { Order } from '@/features/orders/types'
+
+export function getOrders(hasReceipt: boolean): Promise<Order[]> {
+  return apiFetch<Order[]>(`/orders?has_receipt=${hasReceipt}`)
+}
+
+export function deleteOrder(orderId: string): Promise<void> {
+  return apiFetch<void>(`/orders/${orderId}`, { method: 'DELETE' })
+}