Add COD-in-transit summary and received tab to the dashboard

- GET /orders/summary: count and sum of cash-on-delivery for parcels not
  yet picked up (excludes received, refused, deleted/unknown TTNs, paid COD);
  shown as a card above the tabs.
- New «Полученные» tab: orders with NP received codes (9, 10, 11, 106) move
  there automatically, regardless of receipt; 106 is now a final status.

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

backend/app/schemas/orders.py

@@ -122,6 +122,13 @@ class OrderRowOut(BaseModel):
         )
 
 
+class OrdersSummaryOut(BaseModel):
+    """`GET /orders/summary` — сводка над таблицей заказов."""
+
+    cod_in_transit_count: int
+    cod_in_transit_amount: str
+
+
 class OrderGoodIn(BaseModel):
     """Позиция заказа из формы редактирования. `amount` считает сервер."""