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>

backend/tests/test_orders_service.py

@@ -0,0 +1,26 @@
+"""Юнит-тесты чистых хелперов сервиса заказов. Без БД и без сети."""
+
+from __future__ import annotations
+
+from datetime import datetime
+
+from app.services.orders import _parse_crm_datetime, _to_kopecks
+
+
+class TestToKopecks:
+    def test_converts_decimal_string_to_kopecks(self) -> None:
+        assert _to_kopecks("599.00") == 59900
+
+    def test_handles_fractional_kopecks(self) -> None:
+        assert _to_kopecks("12.34") == 1234
+
+    def test_handles_integer_without_fraction(self) -> None:
+        assert _to_kopecks("100") == 10000
+
+    def test_handles_zero(self) -> None:
+        assert _to_kopecks("0.00") == 0
+
+
+class TestParseCrmDatetime:
+    def test_parses_crm_format(self) -> None:
+        assert _parse_crm_datetime("2026-09-20 10:00:00") == datetime(2026, 9, 20, 10, 0, 0)