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/app/services/crm/exo_client.py

@@ -0,0 +1,46 @@
+"""Реальный клиент exoCRM (`GetOrders`)."""
+
+from __future__ import annotations
+
+import httpx
+
+from app.core.config import Settings
+from app.schemas.orders import OrderOut
+from app.services.crm.checksum import compute_md5sum
+from app.services.crm.client import CrmError
+
+
+class ExoCrmClient:
+    def __init__(self, settings: Settings) -> None:
+        self._base_url = settings.crm_base_url
+        self._api_key = settings.crm_api_key
+        self._secret_key = settings.crm_secret_key
+        self._shop_key = settings.crm_shop_key
+        self._sid = settings.crm_sid
+
+    async def get_orders(self, *, status: str) -> list[OrderOut]:
+        body = {
+            "apikey": self._api_key,
+            "object": "Orders",
+            "method": "GetOrders",
+            "params": {
+                "sid": self._sid,
+                "key": self._shop_key,
+                "Status": status,
+                "ReturnGoods": True,
+                "ReturnTotals": True,
+            },
+        }
+        body["md5sum"] = compute_md5sum(body, self._secret_key)
+
+        async with httpx.AsyncClient(timeout=30) as client:
+            response = await client.post(self._base_url, json=body)
+            response.raise_for_status()
+            data = response.json()
+
+        if data.get("status") != "OK":
+            errors = data.get("errors") or {}
+            message = "; ".join(f"{code}: {text}" for code, text in errors.items())
+            raise CrmError(f"CRM вернула ошибку: {message or 'неизвестная ошибка'}")
+
+        return [OrderOut.model_validate(order) for order in data.get("result", [])]